Verify to validate
When planning and implementing energy saving projects, verification of the savings achieved is becoming increasingly important to end users. Geoff Newman of Sabien Technology explains how building services engineers can address this requirement.
When end users investigate ways in which they can save energy they are often attracted by retrofit technologies that require relatively little capital investment, while delivering a sensible return on that investment. However, they also need to be sure that any such project delivers the benefits that were anticipated, often to justify their actions to senior management or to gain funding for a wider roll-out of the technology in question.
To that end, it is important to have a validation methodology in place from the very start of the project to ensure that any energy savings can be verified accurately. In this respect it makes sense to work within the International Performance Measurement and Verification Protocol (IPMVP), as this provides an internationally recognised framework for the validation of energy saving projects.
This has clear implications for the building services engineer’s approach to the management of any such projects and companies that do not have their own Certified Measurement and Verification Professionals (CMVPs) are well advised to work with suppliers that do.
In parallel, and at the risk of stating the obvious, it is important to take all necessary measures to ensure the success of the project so that the validation process confirms expectations. This requires taking account of a number of factors that may influence the outcomes of the project.
The current situation
Clearly the first step for any such project is to have a good understanding of how much energy is being used, and ideally where it is being used, in some detail. However, the level of detail will to some extent be determined by the level of metering in place. For example, if gas consumption is only measured for the entire building it may not be possible to measure gas used for heating and gas used for catering separately. Therefore, sub-level metering will provide the most accurate picture on which to base investment decisions. It will also be useful for the subsequent validation of savings through a measurement and verification programme.
Unfortunately, in the real world it isn’t always possible to work with the ideal level of sub-metering but there are ’work-arounds’ that will help to provide a clearer picture. For example, a toggling technique that switches between the running of the retrofit technology on one day and not running it on the next – typically over a period of one month – enables a ‘with and without’ comparison that helps to take account of demand variations within the building.
Choosing the technology
When retrofitting energy saving technologies it is clearly important to ensure that the chosen technology will deliver what is promised. To that end, the technology provider should be able to explain how the product works in a way that makes sense from an engineering perspective and doesn’t try to hide behind technical jargon.
A good example of this is the use of the retrofit technologies to prevent boiler dry cycling. It is a given that the basis of controlling a boiler is to respond to changes in temperature, therefore any technologies that work by artificially lowering the boilers’ temperature set points may compromise comfort conditions.
Similarly, if time is used as the basis of the control strategy – such as delaying the firing of the boilers – this may also impact on temperatures and comfort conditions. In the latter case, if savings are reported as a reduction in boiler run-times, and a two stage or modulating burner is in use, it’s important to be aware that reduced run time is not the same as a reduction in the actual kWh.
The other important issue with retrofit technologies is that they need to work in harmony with existing controls. Returning to the heating systems example, many heating systems will already be linked to a building management system and may also be using weather compensation, demand control and/or boiler sequencing. Any additional controls, therefore, must not interfere with these. Rather, they should add to the energy savings that are already being achieved by the existing control strategy.
Engagement with all parties
The technology that is to be implemented is only one factor in the successful delivery of such projects. In our experience most projects involve multiple stakeholders, all of whom may have some influence over how well the project runs.
For instance, at the start of any such project it will usually be necessary to develop a business case to gain the necessary funding. Inevitably, this will involve the finance or procurement department and in many cases the building services engineers will be asked to help in developing the business case.
Once the project has been approved and initiated, there may be a need to access plant in a number of plant rooms, often in different buildings, so gaining access requires communication with a number of different people.
In parallel, there may be one company responsible for maintaining the boilers and another for maintaining the building management system. Both parties will need to be aware of what is being done and how the technology works. It is important that any changes to the operation of the plant or building are captured and, furthermore, the product being verified is not inadvertently tampered with as this could lead to the verification project being invalidated.
It is therefore very important to identify who all of these people are from the outset and ensure they understand the objectives of the project and the benefits it will deliver.
Of course, where multiple stakeholders are involved this engagement process can be very demanding on resources so it is important to verify that the provider of the retrofit technology can take responsibility for most of these aspects of stakeholder engagement.
At the beginning of this article I stressed the importance of measurement and verification and in the case of heating systems this is especially important because energy consumption will be influenced by variations in temperature. As a result, a simple ‘before and after’ comparison of the energy consumption will not reflect what has actually happened. The energy consumption data must be adjusted to compensate for this using the degree day data supplied by the meteorological office – this will ensure the analysis is accurate.
Most such projects also have to take account of a number of other variables, such as changes in building usage, variation in occupancy, changes to the building fabric or other energy saving projects being carried out simultaneously. In such cases the methodology agreed with the client at the beginning of the project, ideally within an IPMVP framework, should include measures to take account of these variables.
When dealing with changes in energy consumption over longer periods of time (pre, during and post project) CUSUM (cumulative sum) analysis is another useful tool – and one that has been approved by the Carbon Trust.
The principles that have been described here are based on our experience of managing many such projects that involved retrofitting our M2G intelligent boiler optimisation technology. However, the same principles can be applied to any project that involves the retrofit of energy saving technologies to existing systems.