An Energy Services Company (ESCO) is a commercial business that “will identify and evaluate energy saving opportunities and then recommend a package of improvements to be paid for through savings”.[1]  Performance Contracting with an ESCO can be a very powerful tool for a company with energy saving opportunities but no upfront cash or financing options to implement the projects.  An ESCO is a one-stop shop for energy opportunity identification, quantification, financing, implementation, staff training and a guarantee that the savings will cover the costs of the project.  For a business, the bottom line is that one’s annual operating costs will not increase, because project financing and the cost of the ESCO are both covered in the energy and maintenance savings realized by the project.  In addition, the ESCO assumes the risk of under-performance.  If the savings are not achieved, the ESCO is responsible for covering the difference.

The ESCO Process

1. Initial Assessment
The process starts with a preliminary assessment by the ESCO to determine what energy saving opportunities reside in the building. Often opportunities are items such as boiler or chiller modifications, motor replacements, lighting retrofits, and the installation of a building control system. This initial assessment is performed at no cost to the owner.

2. Energy Savings Performance Contract
If both sides feel sufficient opportunities are identified in this initial assessment, the owner and ESCO begin with an Energy Savings Performance Contract.

Energy Performance Contracting: Before and After Improvements. Source: Energy Sources Coalition - http://www.energyservicescoalition.org/resources/whatis.htm

This contract initiates the comprehensive investment grade audit and details a variety of stipulations regarding construction, leases, performance guarantees, rate risks etc. The contract also states how savings will be determined: whether they are stipulated, in which case no field verification is required, or a more rigorous Measurement and Verification Protocol will be applied to verify savings over the course of the contract.

If the owner declines the implementation of the construction after this point in the process, the owner is liable for the audit costs (typically $50-$80k). If the owner proceeds, then the audit costs are rolled into the contract and the owner incurs no upfront costs.

A Performance Contract value is typically in the $1,000,000 range or up and lasts for 8-10 years, although some innovators are looking at how to apply the ESCO model on smaller projects with less savings potential. During the contract time period the energy savings are used to pay off the investment so the annual out-of-pocket costs for the owner do not increase.

3. Financing and Return on Investment
Project financing is typically arranged through a third party who is familiar with the ESCO and can value the savings guarantee appropriately. When financing costs are identified, a full contract delineating the efficiency measures, cost savings, construction costs, ESCO costs, financing costs and guaranteed savings is developed for a complete picture of the return on investment.

4. Construction and Staff Training
The ESCO is usually responsible for the entire construction process. In some cases, the contracts can allow for the owner to manage construction providing more transparency in the process. The owner’s involvement is typically to coordinate the work within their facility to minimize disruption to work flow and occupants. The ESCO uses commissioning to validate construction and provides training to ensure the maintenance staff understands how to operate new building systems. The owner then ensures proper maintenance of the equipment throughout the contract period.

5. Savings Verification and Annual Costs Reconciliation
The ESCO verifies savings that are not stipulated using meters and utility and maintenance billing analysis to verify the project’s overall savings. The return on investment calculations quantify the net operating cost gain or loss to the owner. The loan that funds the project is paid from the savings. In the event that the savings are not adequate to cover the loan payment, depending on the circumstances, the ESCO will pay the difference based on the savings guarantee. The ESCO typically receives a significant share of the savings in excess of the loan payment to cover their costs and help mitigate risk. If the project produces excess savings, we have seen owners reinvest in their building to allow for capital upgrades that may otherwise be unfeasible or accelerate the pay off of the project’s loan.

Advantages and Disadvantages of Performance Contracting

The most obvious advantage to working with an ESCO on a Performance Contract is that the owner does not have to take out a loan or invest any money upfront and that the return on investment is guaranteed. It is a very secure investment, with limited liability and financial risk. It produces a detailed assessment of the energy saving opportunities of the building, as well as providing a turn-key construction process that does not require the owner’s involvement.

The disadvantage of an ESCO’s involvement is that, in order to maximize profits, ESCOs often focus on lower cost measures with easy-to-predict savings and they often do not take a comprehensive approach which will provide deeper savings, but at a significantly higher cost. For example, lighting and mechanical system modifications will be suggested, but building envelope improvements (which typically have a very long payback period) will not be included. This is a lost opportunity in the sense that lighting measures with a 9-month payback can help reduce the envelope improvements’ 8 year payback when bundled together in one package. Another obvious disadvantage to using an ESCO is that it costs more money than if the owner would perform the project themselves. The ESCO’s overhead and profit are included in the project’s costs. If the owner hires an energy services company to perform the comprehensive energy audit and then implements the project alone (financing and construction), all of the savings will go directly to the owner.

Recommendation

All buildings have energy saving opportunities, even the newest buildings. In our experience the first major step is identifying and quantifying the magnitude of this potential. The most cost effective manner to commence reducing one’s energy consumption is to hire an energy services or commissioning company to perform an audit. (If using a commissioning provider, ensure they have expertise in energy efficiency and can identify opportunities for capital improvements that may exceed the retrocommissioning scope.) From there, an owner can decide the best direction to take. Retrocommissioning is a great vehicle to address energy efficiency and building system performance in order to provide optimal environmental comfort to building occupants. Typically, retrocommissioning is a less costly endeavor; having less than two year payback and does not involve major capital improvements. If energy saving capital improvements with long payback periods are identified, then an energy savings performance contract with an ESCO may be an appropriate avenue to accomplish these additional savings.

[1] http://www.energyservicescoalition.org/resources/whatis.htm

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When as a facility operator you’re looking to reduce data center energy use, it can be difficult to know where to begin in the process of improving efficiency. Regardless of whether your organization operates a large datacenter, or a small server room, you probably face the same question: Should we start by improving efficiency of the actual IT equipment, the supporting systems such as HVAC, or both?

Where to Begin

One effective approach when tackling data center energy use is to begin by addressing load reduction first, followed by improving the efficiency of the equipment that supports/manages those loads. This is analogous to the approach often taken in building systems: when performing a major building renovation including building shell, internal loads (e.g., lighting), and central plant equipment, new central plant equipment should be sized to address the new, more efficient building load, rather than the pre-renovation loads.

To reduce data center loads, several approaches can be taken on the IT side of the equation to significantly affect energy use, some of which can be accomplished without any additional hardware investment. These primarily boil down to two areas: increasing server utilization and offloading capacity to cloud-based data center services.

Server Utilization

According to a guide recently published by the US DOE’s Federal Energy Management Program (FEMP), “The majority of servers run at or below 20% utilization most of the time, yet still draw full power during the process.”[1] Server utilization is effectively how loaded the server equipment is, as a percentage of total capacity. Technologies entering the mainstream over the past decade have begun to make significant inroads in improving server utilization, most notably, server virtualization.

Racks of telecommunications equipment in part of a data center. (Photo credit: Wikipedia)

Server Virtualization

The primary advance which has facilitated higher server utilization rates is a technology called virtualization. In short, virtualization is a method of creating a software version of a physical hardware computer (in this case, a server). From the end user’s perspective (say, a department at a college or a sales team within a company which used to manage their own physical server) the physical-to-virtual conversion is seamless: the end user cannot tell that they have transitioned to interacting with a software version of their server: the interface is identical and performance is not noticeably impacted. From an IT side, however, the new virtual server, which formerly was only running at say, 25% capacity, can be combined with 3 other virtual servers also running at 25% capacity and then can all be placed on a single physical server operating at nearly full load. Effectively, with virtualization, many underutilized servers can be consolidated into fewer physical servers, and significant energy savings can be realized.

While server virtualization is no longer a cutting edge technology, because of relatively long server life spans, a significant amount of low hanging fruit may still exist in any given company’s IT fleet, and accomplishing these savings can be cost a cost effective approach to improved energy performance.

Cloud Services

Many opportunities exist to migrate some or all server processing and/or storage capacity to large, offsite, cloud computing services. Huge, centralized datacenters can achieve extremely high levels of efficiency–typical onsite data centers have PUE (Power-Usage-Effectiveness) values typically between 1.75 and 2.0, whereas large, cloud scale datacenters can achieve PUE’s of <1.2. A wide variety of services exist to meet a range of needs, but some include Amazon.com’s Elastic Compute Cloud (EC2), and Microsoft’s Windows Azure, to name a few.

Cloud Control –This is a picture of the Magellan management and network control racks at NERSC. To test cloud computing for scientific capability, NERSC and the Argonne Leadership Computing Facility (ALCF) installed purpose-built testbeds for running scientific applications on the IBM iDataPlex cluster. credit: Lawrence Berkeley Nat'l Lab - Roy Kaltschmidt, photographer

Not all applications are appropriate for cloud computing transition, and there are tradeoffs which should be examined on a case-by-case basis. For many applications however, significant energy and labor cost savings can be realized in shifting a portion of their datacenter load to cloud services.

Conclusion

There are a range of approaches to saving energy in the modern datacenter and some options may be less capital intensive than others. Consulting with your resident IT geek on possibilities presented by virtualization and cloud computing may be a cost effective place to start reducing energy use in a shorter time frame.

[1] Best Practices for Energy Efficient Data Center Design, US Department of Energy FEMP, March 2011, Page 1: http://www1.eere.energy.gov/femp/pdfs/eedatacenterbestpractices.pdf

As an industry, we provide building operators with efficient heating, ventilation and air conditioning (HVAC) systems as well as powerful building management control systems. Then we expect the operators to run the high-tech HVAC equipment efficiently.

But we don’t give them the tools to answer the fundamental question: “How many ‘miles per gallon’ is my central air handing system getting?” The expectations are implicit, but the tools and basic information for management are lacking. We are not providing energy use feedback in our designs.

Providing such information does not have to be complex or expensive. In fact, the most basic energy use parameter for a fan or a pump, which are commonly fitted with variable frequency drives (VFD) nowadays, is motor power consumption: kW. Every VFD has a “free” built-in kW meter. With over a decade of conducting design reviews, I have yet to see a design engineer call for the motor power to be displayed on the system graphics panel. There is no incremental cost to do so. Why not?

Simply displaying kW next to the fan graphic display provides useful feedback. We can take it one step further for a central variable air volume (VAV) air handler by providing a meaningful performance metric such as kW per 1,000 Cfm (kCFM). This is quite simple: sum the dynamic supply, return (and relief, if applicable) fan kW using the supply air volume. Most VAV air handlers have air flow measurement stations to capture supply air flow. If not, the next best option is to totalize the terminal VAV box air flows.

This kW per kCFM is akin to miles per gallon we use for our cars. Something we all understand. Just like modern cars that display real time mpg, which enables us to learn how to drive more economically, feedback from building systems will enable facilities staff to operate their buildings more economically.

Empowering Building Operators

Now a building operator has information to immediately know the impact of changing a setpoint such as a colder supply air temperature (because the boss in the corner office is complaining).

And other questions in the building operator’s mind can be answered such as:

A graphic from a DDC system displaying fan speed.

• How does my air handler compare to other similar systems?
• Am I using what is expected?
• Has anything changed?
• Am I improving over time?

This is important because according to the Lawrence Berkeley National Laboratory, building energy use depreciates about 2% to 3% annually. Simply providing performance information, even if operators are not actively engaged in reducing air handler energy use, reduces energy use by about 2%.

Real World Answers

I often read articles in technical publications such as ASHRAE Journal, where the author says something like, “We determined changing the supply air temperature increased fan energy by conducting computer building simulation modeling.”

Why simulate? Why not answer the question using a real air handler with its performance metrics displayed? A real system and real answers.

Quick Answers Enable a Faster Response

Operator empowerment from performance metrics enables quick answers to optimizing strategies such as:

• Is static pressure setpoint reset really worth the effort?
• Did the recent change out to cog type fan belts actually improve my air handler performance?

Trending and archiving such performance data can answer other questions such as, “Why is my system using more power than it did three years ago?”

And there are other benefits. For example, a utility offering efficiency rebates for retrocommissioning (RCx) of an air handler will have available a pre-RCx baseline and post-RCx actual benefit. No fancy complex evaluations or calculations – just real world, believable answers.

Isn’t this really management 101? “You cannot manage what you cannot measure.”

Related Articles

Summary Monitoring-Based Commissioning Study [Evan Mills, PhD, Lawrence Berkeley National Labs]

Performance Metrics Research Project – Final Report [National Renewable Energy Laboratory]

Retrocommissioning (RCx) is rapidly growing in popularity as a tool to cost effectively reduce energy use in existing buildings. A recent study by Lawrence Berkeley National Lab showed that commissioning existing buildings yields significant energy savings and can provide a substantial return on investment. Utility programs are embracing the concept and taking a variety of approaches to helping their customers find providers and engage in an RCx process.

Done right, RCx can provide deep and lasting savings within a facility. Unfortunately many projects look to shortcut the process. Focusing on the Investigate and Implement facets of the process may seem to be the shortest route to garnering savings, but it may result in comfort problems, dissatisfied employees, and measures overridden by maintenance personnel, resulting in the owner’s investment not yielding sustained benefits. I’m going to review each facet of the process and explain why it is critical to the success of your RCx project.

Figure 1. The Retrocommissioning Gem

1. Commit
Cx Associates has worked on several RCx projects where the operations and maintenance staff are not on board. The building owner looks to the RCx provider to somehow garner the support of these individuals who have a variety of barriers to the process. Without the commitment of the organization, from top to bottom, a comprehensive RCx process is likely to fail. In most cases RCx providers have engineering backgrounds and do not tend to have the skills to address organizational resistance to the process.

2. Plan
Many RFPs seek to combine the planning and investigation phases. However, there is a clear benefit of defining the scope of the project before commencing the field work and analysis, and this benefit is not always fully understood by building owners seeking to retrocommission their facility. Planning answers the following questions:

• Are there enough savings opportunities in this facility to support RCx?
• If so, where are those opportunities?
• What are the requirements for a successful RCx project?

Once those questions are answered, the RCx provider can develop a plan of attack for the investigation phase.

3. Investigate
This includes reviewing the building documentation, on-site time verifying control sequences and identifying opportunities, as well as office time estimating savings and the costs of implementation, commissioning, training, and verification.

4 & 5. Implement and Commission
These steps go hand in hand – commissioning should not be viewed as an after the fact part of the process, but it is an essential facet of the process. Implementation includes designing and specifying the measures, contracting and installation. The commissioning process includes review of the contractor proposals to ensure the key aspects of the project are understood, verifying installation, and testing for performance before the contractors receive their final payment.

6. Document
Ensure all of the changes are documented in the facility records. Clear operating sequences that are understandable to maintenance staff should be posted in mechanical rooms. DDC graphics must be updated and verified and include a link to the sequences of operations.

7. Train
If the operators don’t understand the concepts behind the system optimization improvements they will override them. Training needs to be extensive enough to address knowledge gaps in the concepts as well as their execution by operations and maintenance staff. In addition, the end users should understand what to expect and how to report issues.

8. Verify
Most building projects are an open loop. Closing the loop and verifying that the project goals are met is essential to improving practice overall. Verify energy savings, comfort, maintenance practices and costs and provide a feedback loop to the parties involved in the project so that the next project will be even better.

Following all of these steps will reveal the true benefits of the retrocommissioning gem. In future blog posts I will explore barriers we encounter to each facet and the practices we are developing to help address them.

Related articles

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What does sound control have to do with energy efficient design? This blog post is the first in a three part series that will explore the intersection of sound and energy efficiency in existing buildings. My early experience as an applications engineer in mechanical systems noise control made me aware of the connection between the built environment and equipment energy use. System airflow requirements and the impact of total added pressure drop of sound control solutions are primary design variables for a noise control engineer. Full scale HVAC aero-acoustic laboratory testing is an integral component of sound control design.

Importance of Sound

The sound environment in buildings is a comfort condition which significantly affects productivity, occupant satisfaction, and our ability to learn. Any design engineer involved in large-scale building projects has had to consider the impact and control of sound. For a building design to be successful, the built environment, including the background sound level, must be usable for its intended purpose. Since air is widely used for heat exchange and ventilation in HVAC design, and air delivered to a space will convey the sound created by the mechanical equipment and duct system components that it encounters, reduction and control of aerodynamic sound has a reciprocal impact on the design and operation of airside mechanical systems.

Good Design

A good design serves the full range of operational requirements at the lowest possible energy and financial cost over the life of the system. Noise is wasted energy. If a system is noisy, energy is probably being wasted. To give an example of where an improvement in energy efficiency also resulted in mitigation of noise, in a recent pro bono design review by Tom Anderson of Cx Associates for a local church, an oversized air handling unit was eliminated in favor of a smaller energy recovery unit. The result was a smaller, quieter, less expensive system that could be located in the basement away from a noise sensitive sanctuary, easily meeting the stringent NC-20 acoustical design target. Thus a good design was reached through control of energy and noise.

Opportunities in Retrocommissioning (RCx): What to Look For

How can you make low cost modifications to airside distribution systems that will improve occupant comfort and reduce energy costs? From a noise/energy control standpoint, it is generally effective to start at the source, for example, by reducing fan speed, lubricating bearings, and making sure belts are properly tensioned. Even if your building does not currently have variable speed fans or a sophisticated building management system, significant annual savings from improved air distribution design may still be a low cost opportunity.

Reducing unnecessary static pressure losses (such as “system effects”) in an existing constant volume system can improve opportunities for lower fan turndown resulting in quieter sound levels and lower energy use.

Figure 1 - Unnecessary System Pressure Drop Reduces Airflow, Requiring Higher Fan Speed to Reach Design CFM, 2009 ASHRAE Handbook Fundamentals, p21.12

If a system is noisy, it should be on the top of the list for a review of energy efficiency measures, but even if noise is not excessive, there may still be unnecessary losses associated with construction and balancing of your existing systems. Did the balancer add system pressure drop by closing dampers to meet the engineer’s specified operating point, instead of reducing fan speed? If so, the system could be rebalanced for lower fan speed by opening dampers and installing a VFD or resheaving the fan. Did the HVAC contractor install an abrupt transition immediately after the fan? Alternative routing or fan reorientation will mitigate high head losses in blast areas.

Figure 2 - Blast Area High Velocity Profile, High Head Loss, 2009 ASHRAE Handbook Fundamentals, p21.12

In another example, a standard sound attenuator may already be installed, adding 0.25” w.c. static pressure drop to the system, permanently, at all times. If such an attenuator is installed in a non-ideal location due to difficult site conditions, this pressure loss could increase by a factor of two or more due to airflow turbulence interactive ‘system’ effects [1].

Figure 3 - Eliminate Unnecessary System Pressure Drop

It may be possible to replace the sound attenuator for a few hundred dollars with one that adds no pressure drop, or to relocate it to a more favorable location. Potential annual cost savings for eliminating 25% of system pressure drop for an existing mid size constant volume fan may be comparable to average savings for an existing similarly sized VAV supply system with static pressure reset control, assuming an average CFM load of between 75% and 80% design CFM. While 75% to 80% may be on the high side for a typical VAV system, the potential savings for reduced static pressure on a constant volume fan can be in a similar range, 15,000 to 20,000 kWh ($1,500 to $2,000) per year.

Figure 5 – VAV Typical Operating Range A Practical Guide to Noise and Vibration Control for HVAC Systems, M.E. Schaffer, ASHRAE

Make the Most of your RCx Investment

In summary, low cost improvements could result in significant energy and cost savings for a mid size constant volume supply fan, typically paying back in less than five years, even for systems without direct digital control.

An awareness of sound control issues and methods can help your existing building RCx project maximize energy and cost savings and occupant comfort. Even if a system is equipped with automatic controls, a walkthrough of the physical systems and a drawings review including air distribution systems are essential before sitting down with the controls contractor to ‘tweak’ the systems. The danger of relying on controls alone to reduce energy before understanding the actual as-built existing systems is that your RCx effort may only scratch the surface of potential savings.

[1] Application of Manufacturer’s Sound Data, ASHRAE, 1998

First, the fine print. When talking about condensing boilers, caveat emptor – Latin for “buyer beware.” A phrase usually associated with real estate transactions is highly applicable to the purchase and application of “high efficiency” or condensing boilers. There’s no definition of the word “high” when it comes to “high efficiency” boilers.  Usually, these are boilers whose construction allows them to operate with lower water temperatures than traditional boilers.  This allows them to, in theory, extract more of the useful energy from the fuel source (usually natural gas or propane) than the traditional boiler would.  Notice I said “in theory.”  I’ll get to that shortly.

Condensing Boiler Operation

I’m going to be brief here because there are a lot of readily available resources that explain condensing boiler technology. Basically, condensing boilers are designed to take advantage of the latent energy available in the exhaust flue gasses. By allowing the temperature of the return water to go below roughly 130° F this causes moisture to condense out of the flue gas. That moisture is vapor before it condenses and by turning a vapor into a liquid, useful energy (heat) is given up in the process. In this case, it’s given up to the hot water you’re trying to heat your home or building with. It’s the harvesting of this latent energy that increases the efficiency percentage of a boiler beyond the low 80’s.

This isn’t an all or nothing deal, however. The vapor in the flue gas only starts to condense at about 130° F return water temperature. You get very little increase in efficiency beyond non-condensing operation at this temperature. Slightly above a 70° F return water temperature is when you hit the 98%-99% efficiency numbers you often see advertised. The increase in efficiency is roughly linear with a corresponding drop in return water temperature. Therein lies the key to getting the most out of your condensing boiler.

Factory Controls — Know What You’ve Got

For the sake of this discussion, I’ll assume that these are stand-alone heating systems that are not tied into a building management system (BMS). Many of the same principles, though, apply to BMS-tied boilers as well.

Boiler manufacturers provide factory default hot water supply temperature (HWST) reset control settings that rely on an outdoor air temperature (OAT) sensor being present. The reset control changes the HWST set point the boiler maintains as a function of OAT; as OAT goes up, HWST goes down. The idea is to try to achieve condensing operation at some point during the heating season and it’s possible because at higher outdoor air temperatures, the amount of heat needed from your heating system goes down.

Of particular note is that an outdoor air temperature sensor has to be connected to the boiler to reset the hot water temperature. If no sensor is present, all boiler manufacturers have a HWST factory default setpoint of between 176° F and 194° F (roughly). Why? Hot water temperatures within this range will generally satisfy a large majority of heating systems’ demands and if nobody installs and connects the OAT sensor, the boiler manufacturer wants to be sure their product delivers heat. Without the OAT sensor, the boiler will never condense and its efficiency will average between 80% and 85% in most cases, no better than a good non-condensing boiler. The extra capital investment spent on a condensing boiler was just lost.

OK, so let’s assume an OAT sensor is present. Figure 1 is a chart showing the factory default, out-of-the-box, hot water supply temperature (HWST) reset schedule as a function of OAT. Figure 1 represents five different, small-scale condensing boilers (up to about 2.0 MMBTUH) from varying, well known manufacturers. Let’s take Boiler #1 as our example. This boiler starts to condense when the OAT is above about 56° F. Now, for example, between 55 and 65 OAT in Burlington, Vermont (a cold climate, ASHRAE 6 A / B), that’s still about 2290 hours or 33% of the hours the boiler will operate. Not bad, but it leaves 67% of the time when the boiler is not condensing. The other manufacturers have more aggressive curves to varying degrees, but there is still an opportunity with most to take better advantage of the more efficient operation due to condensing.

Of note here is that Boilers 2 and 3 already have quite good curves out of the box. Before making any tweaks, be sure to know your starting point.

Figure 1. Factory default curves with OAT sensor present shows significant opportunity for optimization with some and very good “out of the box” performance for others.

How to Do Better – Planning

It’s important to start with the end, and end with the beginning; in this case, start with the equipment that delivers heat to the space, like a radiator or finned tube radiation aka the “terminal device.”  Typically, these are designed to deliver the peak heating required to the space using somewhere around 18o° F water.  That peak is only for roughly 88 hours (1%) of the entire year when based on ASHRAE design data and, frankly, that peak is almost always designed to be higher than truly necessary; the system is oversized.  Reducing that HWST by just 20 degrees changes the reset curves and lowers the OAT at which the boiler begins to condense.  Using Boiler #1 as an example, this makes the condensing OAT about 46° F which increases the number of hours to about 3512 or 50% of the time.

Figure 2 Lowering the maximum HWST results in 17% more hours of condensing operation in this example. Existing systems are typically oversized, allowing for the lower HWST and new systems can be designed accordingly.

In new construction the terminal heating device can easily be selected to satisfy the design condition with 160 vs. 180 degree water with little or no impact on physical size and minimal impact on first cost. In fact, the simple payback for fuel savings vs. additional terminal device cost will very likely be less than four years and in most cases be between one and two. In existing construction, it’s likely the heating system is oversized enough that the same approach can be taken and the payback is immediate because there’s no additional capital cost. With the terminal units designed to use a maximum of 160° F water, you’ve just increased the hours of condensing operation.

By designing for lower maximum hot water temperatures, engineers and designers can take more advantage of condensing operation and the commensurate increase in boiler efficiency.

How to Do Better – Implementation

Once the heat delivery components are taken care of, making the changes at the boiler controller is where the rubber meets the road. Changing the operating parameters will be in the user’s manual and will be more or less daunting depending on the make and model of the boiler, but in most cases will be fairly straightforward.

The simplest approach involves changing one parameter on your boiler controller – the maximum HWST. This changes the shape (the slope, really) of the reset curve, lowering the OAT at which condensing begins to happen. This is what’s represented in Figure 2.

But hang on – we can do even better. Rather than change the reset curve slope, let’s shift it to the left altogether. The heat loss from a building varies linearly with the OAT and, as luck (or physics) would have it, the BTU output of typical finned tube or flat panel radiation (the heat delivery devices) varies linearly (more or less) with the water temperature that’s delivered to them. This relationship allows you shift the entire reset curve to the left rather than just lower the maximum water temperature. In the case of Boiler #1, this approach puts you in condensing mode 80% of the time!

Figure 3 shows what happens when you lower the maximum HWS temperature to 160 AND shift the curve rather than change the slope.

Figure 3 Shifting the actual curve results in 47% more hours of condensing operation.

This approach involves changing two parameters on your boiler controller – the maximum HWST and the maximum OAT.  To get this right, you can go back to high school algebra to figure out the new maximum OAT corresponding to the lowest HWST or you can graph the numbers and use a good-ol’ ruler to get very close.

Know Your Boiler’s Controller

I used Boiler #1 as my example because it had the out-of-the box settings that offered the most potential savings.  Of note, though, is that this boiler has three pre-set reset curves, the most aggressive of which has a maximum HWST of only 120° F and puts the boiler in condensing mode 100% of the time.  If you take the time to read the manual, you might find that you can do away with that pesky math or that clunky ruler by simply using an already built in reset curve.  Just make sure the heat delivery devices are sized appropriately.

Conclusion

In order for condensing boilers to realize their potential for increased efficiency, they’ve got to be allowed to condense.  You do that by lowering the hot water supply temperature set point which, in turn, lowers the return temperature as well.  Many boiler manufacturers offer more than one pre-set curve while others allow manipulation of the set points themselves.  In either case, with a little planning and some understanding of how the boiler controls actually work, you can increase the seasonal efficiency of your boiler with little or no added first cost.  Who can say no to that offer?

There are many opportunities to improve computer datacenter energy performance, whether you’re operating a small server closet, or a large datacenter in a Fortune 1,000 company. But the key to tackling energy use in datacenters is measuring and tracking energy performance over time. Relevant measurement of energy performance over time is feasible now, but that has not always been the case.

Datacenter (Photo credit: Wikipedia)

Moore’s Law and Koomey’s Law

In the mid 1960’s, Intel cofounder Gordon Moore predicted that the number of transistors that can be cost effectively fit on a computer chip doubles approximately every 18 months. This predicted trend, known as “Moore’s Law”, has proved remarkably accurate and associated computer capabilities have tracked closely to this trajectory of growth, even to this day. This rule of thumb for growth applies to computational speeds as well as memory capacities—and anyone who has purchased flash memory for say, a digital camera, in the past decade knows this price-per-capacity over time relationship to be experientially true; a 1 gigabyte flash card that could be purchased for $100 in the mid-2000’s is nearly free today.

So what relationship does this rapid growth in compute capacity have on trends in computer energy efficiency? Historically—and especially in the past few decades with the increasing transition to mobile computing platforms, such as handhelds and laptops—market-driven energy efficiency concerns have been as important as processor speed. The industry quickly found that fast and powerful mobile hardware (e.g., smartphones, laptops) with a huge energy footprint will not sell if they only have a few hours of battery life. And it turns out that historically, a relationship remarkably similar to Moore’s Law has held for the relationship between processor capacity and energy consumption. According to research by consulting professor Jonathan Koomey of Stanford University, for a fixed computational load, energy use has declined by 50% every 18 months — a trend that holds historically true back to some of the first computing hardware in the 1940’s. Others have dubbed this “Koomey’s Law,” though Koomey has not.

Where is the Return?

Despite these drastic improvements in raw compute efficiency, impacts of this trend on datacenter energy consumption have been slow to materialize. In a 2007 EPA report to congress examining datacenter energy use[1], researchers (led by Koomey’s work) reported that US datacenter energy requirements had more than doubled in the period between 2000 and 2006. Based on this trend, the report projected another doubling in datacenter energy use by 2011—with an annual energy use estimate of 100 billion kWh, and a peak demand of 12 gigawatts. To put this peak demand in perspective, the nation’s largest baseload nuclear power plant, Palo Verde, operated by Arizona Public Service, is rated at 3.3 GW. Figure 1, below is a graph that presents historical and projected datacenter energy use, as presented in the 2007 report to congress.[2]

Figure 1 - Datacenter Energy Use Trends

In an updated examination of these datacenter energy use trends[3], commissioned in 2011 by the New York Times, Koomey found that these 2007 projections were overestimates—rather than more than doubling datacenter energy use, the increase in the US was only 36%, and only 53% worldwide. The reasons for this lower-than-projected increase in energy use are several-fold, though interestingly, increased compute efficiency was not the leading factor. Instead, the economic slowdown, as well as increased server utilization (more work done by the same number of servers) were likely the primary drivers. In fact, during this period, energy use per server continued to increase, but through improvements in virtualization—or running multiple software instances of a server on a single physical server—server utilization rates were able to be increased significantly, thereby reducing the comparative effects of underutilized server standby losses.

Start With Performance Metrics

Despite the macro trends in datacenter energy use, most facilities operators are likely to see a continued and significant increase in energy requirements for datacenters, though with that said, most facility managers (other than large-scale datacenter operators) may not even know how their energy performance has trended, due to a lack of data—often the only information to work with is that provided by the “house” power meter. Additionally, tracking datacenter energy performance can be difficult—largely because the datacenter is comprised of a set of systems: HVAC systems (cooling), networking hardware, lighting, humidity control, uninterruptable power supplies, and more—all of which affect performance and have interactive effects. Plus there is the question of “what do I measure, and how?” In an effort to create standard performance metrics across the industry, The Green Grid, an industry nonprofit, was created to establish standards[4]. The metric which they advocate using (which is the industry-accepted metric at this time) is Power Usage Effectiveness (PUE). The PUE is the ratio of the total site power (computing plus overhead facility power) to computing hardware power. There is some variation in where the “boundary” lines are drawn in this calculation, and The Green Grid, as an industry organization, provides a looser definition of these boundaries. Figure 2, below, depicts Google’s version of what is included in the calculation, and is more consistent with Koomey’s level of rigor in his 2008 report, The Science of Measurement: Improving Data Center Performance with Continuous Monitoring and Measurement of Site Infrastructure[5].[6]

Figure 2 - Google's Depiction of Datacenter Energy Users

Estimates for PUE values for US datacenters were between 1.83 and 1.92[7] — in other words, for each kWh used by datacenter hardware, between 0.83 and 0.92 kWh were used for supporting systems. For large scale “cloud” datacenters, such as those operated by Amazon, Google, IBM, etc—a tremendous amount of effort has been expended on optimization and efficiency. As a result, they are currently self-reporting PUMs as low as 1.19. These efficiencies are possible because the compute and energy densities allow for very fast payback for measures to improve performance.

Conclusion

There are many opportunities to improve datacenter energy performance, whether you’re operating a small server closet, or a large datacenter in a Fortune 1,000 company — many IT-side approaches exist to improve server utilization, new, more efficient server equipment enters the market all the time, and new standards from ASHRAE (the American Society of Heating and Refrigeration Engineers) provide updated guidance on optimizing cooling and other HVAC efficiency for datacenters. And all of these approaches will be examined in more detail in future blog posts. However, the most important first step in tracking energy use in datacenters is measuring and tracking energy performance over time. In fact, this approach in general is one that we strongly advocate to our clients in many areas of building operations—without data, making smart and effective decisions to improve performance (and reduce cost) are difficult, if not impossible.

As an HVAC design engineer and an energy analyst, I was intrigued by the building commissioning process when I first came to work for Cx Associates. The building commissioning process is where the theoretical design world meets the reality of “how does my building actually work”?  Designers typically don’t get this feedback; they must move on to their next job as soon as the design is complete.  In addition, design engineers almost never get on the job site during construction to see design issues first hand, nor do they typically receive feedback on how the building operates after occupancy.  This lack of feedback is recognized as a lost opportunity for continuous improvement, but it’s a reality.

Commissioning is in the Field 

Emily Cross, Engineer at Cx Associates, performs commissioning in the field

I now work as part of a team with very experienced commissioning agents who spend almost half their time in the field answering exactly this question: which designs and system approaches work, and which ones fail to deliver the expected performance? These commissioning engineers are physically following duct work and piping as well as calculating building loads and identifying energy efficiency opportunities.  These engineers know what problems arise and what options are available, for example, when balancing valves are inoperable because they are against the 36”x16” duct that needed to be re-sized to fit into a 24” plenum with a sprinkler line in the middle of it.

Commissioning Design Reviews Provide Feedback

Commissioning design review notations on a mechanical drawing

This hands-on experience is extremely valuable to a designer. Working as part of a team, the commissioning agent can provide real-world feedback during the design phase on such things as performance or maintenance issues with the placement and selection of equipment. In addition, commissioning engineers with design experience are equipped to identify design improvements that can save the building owner money by reducing operating energy costs over the life of the building, and lowering first costs by proper sizing of equipment. For example, a commissioning design review may identify opportunities for pressure or temperature reset controls to reduce the flow of a constant flow domestic hot water or a heat pump loop, saving thousands of dollars in annual energy costs and adding minimal up-front investment. Oversized HVAC equipment cycles frequently, creating noise issues and shortening equipment life, as well as increasing the upfront and operating cost to the owner. A commissioning design review can serve as a check to make sure the engineer worked with the most up to date architectural plans for the building shell when calculating the energy load to ensure properly sized equipment.

Building on Each Others’ Skills within a Design Team

We all want to keep improving our competency.  In addition to standard avenues for professional development such as seminars, classes and conferences, I have found the commissioning agent’s hands-on experience to be invaluable for furthering professional development. Commissioning agents have the opportunity to review and field test numerous designs from various engineers and can bring ideas learned from other projects to the design review.

The entire design team – architects, design engineers and commissioning agents – can learn from each other, as we each approach the project from unique perspectives and bring different experiences to the process.  A collaborative approach and a team spirit will improve the current design as well as build on everyone’s skills for future projects.

Related articles

• How to Present Your Commissioning Design Review Comments Convincingly (buildingenergy.cx-associates.com)
• Building Retrocommissioning: What Is It and Why Should You Care? (buildingenergy.cx-associates.com)
• The Leap: Building Enclosure Commissioning…a LEED Prerequisite (pieforensic.com)

What is light pollution? It’s light that goes where it is not useful. The human race evolved with dark skies at night. The advent of electrification has lead to a proliferation of nighttime lighting that we use to help us find our way and to increase our security in the dark.

Courtesy: International Dark Sky Association

The Problem

Unfortunately our approach has been to throw lots of electric energy away by lighting the sky as well as the areas we seek to illuminate. Light flows without restriction across property lines, we bounce light up off parking lots and roadways, and in some cases outdoor areas are illuminated to levels that allow people to read outside at night. While all of this light may give us a sense of security, it is affecting our health, the health of the ecosystems in which we live and is obliterating our connection with the night sky.

I am fortunate to live on a dirt road in Vermont. While I’m only 12 miles from Burlington, Vermont’s largest city, I can walk down my road on a clear night and see the Milky Way. But, as I look to the north, the sky is aglow with the reflected light from Burlington’s night cityscape. And, the use of night lighting is rapidly expanding out from the city into the suburbs and rural surrounds. Views of the Milky Way have been lost to most Americans and it is rapidly fading from view for the rest of us!

The Solution

We have the power to take back the night sky without risk to property or safety. Here is what is required:

1. Shine night light where it is needed. Flood lights shoot light straight out into space without shielding. This creates glare, which is proven to REDUCE the effectiveness of night lighting. Use shielded lights that shine light directly onto paths, doorways or other targets, without flooding the area and blinding people who are approaching or passing the site.
2. Only use as much light as required. The human eye and brain evolved with dark nights. We actually see amazingly well at night when there are not bright lights all about. Keeping night light levels low allows people to see more naturally at night using our peripheral vision. Low light levels minimize the amount of light that gets reflected into the sky off of the ground.
3. Control lights so they are normally off. Studies have shown that occupancy-based control of security lighting INCREASES its effectiveness. If your site requires security lighting, use occupancy sensors to reduce light pollution and increase security. Imagine this scenario – the local school and its ground are illuminated by flood lights whenever it is dark. The neighbors and the police are accustomed to the high light levels and vandals can easily hide in shadows. The same lighting, normally controlled off, provides a clear indication when someone is in the area. The neighbors will pay attention when the lights go on and the local police will be alerted to inspect the site more closely for miscreants. Keeping the lights off most of the time makes the area less attractive to vandals!

There are numerous web-based resources on the health and environmental impacts of night lighting as well as resources for how to improve our practices. LEED includes credits for appropriate night lighting. Recapturing the energy we are currently throwing away with poorly designed night lighting is an easy first step in reducing the environmental impact of the developed world.

Image courtesy of International Dark-Sky Association

Related articles

• Look Up at the Night Sky For a Change – video (ecology.com; TED video)
• Where Are The Darkest Skies in the World? (unastronomy.com)
• Too Bright, the Night: New Film Tackles City Light Pollution (far2fresh.com)
• Dark Skies (acrosstheuniverseinnotime.com)

Anyone involved in the Measurement and Verification (M&V) of building energy savings has encountered Stratified Random Sampling (SRS), a statistical tool used to handle the huge volume of data from the large number of projects and measures in a typical building energy research effort. From calibrated energy modeling to program evaluation and from the field through to the whitepaper, the use of applied statistical principles will simplify and improve the accuracy and defensibility of your M+V work.

Resistance

Now, at first glance, what could go wrong? Engineers are smart and like math, right? However, the reality of seeing a statistical sampling plan through from start to finish can go against the grain for a typical engineer. Here’s a look at why this is an issue in for Measurement and Verification, and what you can do about it.

Why Sampling?

Consider an example project: an efficient lighting retrofit in a school. You are the lead engineer responsible for evaluating the actual energy savings realized in a lighting upgrade. Imagine that this is one of a dozen similar projects that you are responsible for addressing in a relatively short timeframe.

Chances are you will be given a list, by a statistician, with a few dozen different efficiency measures, all with different levels of use to be verified, including new fixtures in the gym, high performance lights in three kinds of classrooms (60 rooms total), the library, office, and auditorium, as well as new LED parking lot fixtures.

It will begin to dawn on even the most intrepid engineer that there may not be enough time and metering equipment available to complete their evaluation in a timely fashion with the level of engineering rigor one might prefer. Enter statistical sampling.

The Sampling Plan

Below is an SRS sample size calculation for a generic school lighting project. For each usage group, the estimated power or energy savings and the quantity of light control switches are used to obtain the number of ‘tests’ required for an acceptable level of statistical accuracy and precision. Note that instead of metering all 180 classroom lighting circuits, sampling allows us to meter only eight and still achieve valid results!

Figure 1 - Sample Size Calculation

The Site Visit

You check in at the front office and successfully complete the field portion of your evaluation, installing the specified number of loggers in the exact random locations shown on the floorplan. The installed equipment is exactly as documented in the project file.

Figure 2 - Installed Logger Documentation

The Analysis

After all the energy loggers have been successfully retrieved two weeks later it is time to hunker down for the analysis. This is where an engineer begins to break faith with the sampling methodology. After all, now that we have The Data, hasn’t sampling reached the end of its useful life? However, for the sampling plan to be effective, it needs to be utilized in the final analysis too.

Figure 3 - Classroom Sample Group Average for 24 Hour

For example, in the Classroom Sample Group graph above, the lights are on 80% of the time between 7 and 8 am, on average. However, since the Classroom 1 energy logger measured that the lights are always on 100% of the time between 7 and 8 am, it can be difficult for an engineer to use the 80% number in their savings calculations for Classroom 1. Yet that is what an SRS approach requires.

In another example, we may have introduced bias on site by choosing ‘the best’ or most convenient metering locations, rather than using random numbers to choose meter locations, as required for SRS. This may result in overestimating, or underestimating, evaluated classroom energy savings.

 Statistics vs. Engineering

The reason following through with an SRS approach can be a challenge is that engineers have learned to rely on their judgment, and in fact have made a career of it. Codes of ethics generally prevent us from expressing a definitive opinion regarding events about which we have no direct knowledge, at least not without a defensible reason. Statistics, on the other hand, has everything to do with drawing precise conclusions about real events, such as lighting usage in a classroom that was not measured, using no judgment or reasoning, using only a random number approach.

If an engineer has been told that ‘no one really uses that room,’ and it was found locked with the lights off, it can take some convincing to persuade them to take measurements in that room. From the statistical point of view though, if the sampling plan was prepared correctly, it does not matter whether a particular room is used all day every day, or only twice every other Sunday. What is important is that the room was randomly chosen without bias, and not out of convenience, since that very randomness is what establishes the validity of the energy savings for the SRS project.

Conclusions

It may be helpful for building energy engineers using SRS for Measurement and Verification to keep three things in mind:

1)     If site conditions are truly inconsistent with the sampling plan, the engineer can and should exercise their engineering judgment by re-sampling the project on site.

2)     Remember that the metering results might surprise you! If you already knew the answer, you wouldn’t need to meter it.

3)     Trust the methodology. Statistics is widely accepted by many as a valid approach. Strike a balance between a healthy level of professional vigilance in the interest of the highest public good, and trusting that your approved sampling plan has captured the primary variables of interest, for the purposes of an energy savings calculation.

In summary, the more we can learn about when, how, and why, buildings use energy, the better we can control it. Using SRS will allow you to stay ahead of the curve, and be the first to predict trends accurately enough to specify optimal energy control solutions, without depleting your time and financial budgets.