Seeing the bigger picture

25 June 2012

Gauging the success of an energy-saving project can be trickier than many people realise. *Tony Willis explains why it’s important to see the bigger picture and learn from the experience of others.

Many organisations that invest in a project to save energy will want to quantify the energy savings once that particular initiative has been implemented. There are many possible reasons for this, including evaluation of a particular technology for possible wider use, calculating return on investment or contributing to sustainability reporting - or all of these.

Whatever the reason, the key thing is clearly to ensure that the results are meaningful, and there are many factors that can impact on energy consumption and skew the measurements. These include changes in building usage, other energy-saving initiatives in the same building and weather patterns. So it is vital to isolate the influence of these other factors on the data if any evaluation is going to be meaningful and useful – and that means seeing each initiative in the context of the bigger picture.

This is a general principle that applies to all energy-saving projects. However, we can illustrate the principles by considering a product that has been retrofitted to commercial boilers to reduce their energy consumption – by controlling wasteful boiler dry cycling for instance.

In this scenario, it makes sense to compare gas consumption before and after the product has been fitted – and with heating it makes sense to compare similar times of year. Nevertheless, as the last few winters have clearly demonstrated, temperatures can vary considerably so it’s important to use the degree day data produced by the Meteorological Office. Even then, many buildings experience localised weather variation that is different to the nearest weather station so it’s also important to take account of local conditions, such as frost hollows.

Nor is weather the only thing that might influence heating systems. For example, many organisations have introduced flexible working practices that reduce occupancy levels in their workspaces, so that internal heat gains are lower and space heating demands may increase. In buildings with a loading bay, an increase in inbound or outbound goods may result in greater heat losses because the loading bay gates are open for longer periods so more heat escapes the building.

Or there could be an initiative to encourage staff to cycle to work, which then increases hot water demand for showers. So it’s important to adopt a ‘systems thinking’ approach, recognising that heating and hot water systems don’t operate in isolation from other activities in the building.

Also, there may have been other energy-saving initiatives introduced over the same time period – such as improving insulation. So it’s vital that those responsible for energy consumption in the plant room also have awareness of what else is happening in the building.

The right measurement

The other issue, of course, is the accuracy of measurement. Many organisations now use Automatic Meter Reading (AMR) but this tends to be a ‘gate measurement’ that only covers overall consumption. For instance, it may tell you how much gas is being consumed but not break it down into heating, catering etc. So if staff numbers in the building have increased and the cafeteria is producing more meals, this can increase overall gas consumption but AMR won’t typically identify where that increase is.

All of which means that evaluating the success of an energy-saving initiative is more complex than many people first realise. It can be simplified by only carrying out one initiative at a time, so there is only one variable, but that also means delaying the potential cost, carbon and energy saving benefits.

The other option for making life easier and ensuring a successful project, particularly with retrofit technologies, is to research the options carefully in advance and check the track record of each of them. If other organisations have already been through the evaluation process and proved that savings will be achieved, you’re half way there.

*Tony Willis is Technical Sales Director with Sabien Technology