Understanding the problem

The editor of this newspaper has asked what our industry should be doing to be more energy efficient, and whether we have the products on the market to meet our efficiency needs. My answer may surprise you.

The uncomfortable truth is that it’s often very difficult to accurately assess how energy efficiency compares between products. This is because of unrealistic test conditions, unrepresentative lab test methodologies, and a lack of data about real-world energy consumption. If we look at these issues one-by-one, you will see what I mean.

Unrealistic test conditions

It is very common for systems to be desktop modelled to meet the Building Regulations, the Simplified Building Energy Model (SBEM), BREAMM and so forth, using data based on unrealistic standard test conditions. Whilst it is relatively easy to compare generic equipment (e.g. VRF type A versus type B) it is almost impossibly difficult to cross-compare different system technology types (e.g. condensing boilers versus VRF versus WRF versus fan coils versus chilled beams versus displacement ventilation), since they can have very different standard test conditions and operating parameters.

For example, VRF equipment is tested on the basis of temperature at 27/19oC WB/DB room temperature (as measured under Japanese International Standards now enshrined in BS EN 14511) compared to 25/18oC indoor for WRF equipment. Furthermore, test data can ignore factors such as distribution inefficiencies (for instance five metres separation for VRF) and de-frost/oil return cycles.

Even within generic types, care has to be taken. To illustrate, for the last three years there has been an average difference in published efficiency figures of 15% between the top three VRF manufacturers with their heat recovery models, despite the fact that these have all been tested under the same conditions. If you could offer a 15% energy saving to your customers with almost identical systems at no extra real cost I wonder what they would say?!

Unrepresentative lab result

Another issue is the validity of test standards. Several problems exist. Generous tolerances in standards exist, for example, where volume flow measurements can vary by +/- 10% and temperatures by +/- 1K. Lab test methodologies can mean that a product ends up being optimised to meet the standard, and not for how it is actually going to be used when installed.

Looking at whole buildings, there is the problem of significant differences occurring between designed and actual performance. Building services designers often make claim that the reason for this is that the occupancy density, building use and occupancy times are all different from their own assumptions. This can be a legitimate reason, as recently revealed in the review of the Building Schools for the Future initiative, but it can hide the real problem – that the building services or building fabric are simply not performing as well as they should, for whatever reason.

Performance feedback is needed

The industry desperately needs to compare predicted energy consumption with actual energy consumption. This requires longer-term relationships beyond project completion, in order to obtain feedback, which then is passed back to the manufacturer. Performance values can then be compared incorporating all relevant de-rating factors. Coefficients of Performance and Energy Efficiency Ratings can be misleading; actual, measured normalised energy usage is not. If the industry was armed with the correct data, this could be fed into realistic whole-life costing calculations.

I find it worrying that very few articles are ever published advising of actual measured and authenticated energy savings (that is to say against some sort of recognised independent control tests) from the plethora of equipment available and the advertisements these generate.

The industry really needs to engage with end-users, encouraging them to apply the time and temperature control facilities, which are often provided but not used. Equally, suppliers need to provide what the customer really needs, and not what we think they need.

Make better use of existing products /b>

It’s easy to cover up any market imperfections by requesting yet more products. This is not the solution. We first need to understand the dynamics of the problem.

Moreover, considering the severe time and hence money constraints (e.g. design fees) we all face, I wonder if we even have the time, right now, to adequately investigate, evaluate and hence commit to products and technologies which already exist, let alone look for new ones.

There are plenty of efficient products on the market but we have to seek them out and apply them correctly. We also have to accept their first cost may be a bit higher but there are enduring benefits to the person that pays the bills and society in general.

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