THE PROBLEM WITH BEMS?

Julian Miller, Director of controls specialist AEC looks at how BEMS systems are at the core of the energy efficiency problem in many buildings and how they can become a crucial part of the solution.

If I said that 90% of heating and ventilation control systems in buildings were inadequate I am sure that many of you would be at least a little alarmed, particularly if you have ever been responsible for specifying, installing, buying, selling or running such a system. You have apparently bought, sold etc. a system that has a nine-tenths chance “inadequacy”. So unless you are part of the minority you could stand accused being involved with a bit of a turkey!  Well the bad news is that according to CIBSE you are, just look at their General Information Report 40 and go to the beginning, paragraph 1.1 states, and I quote: -

" It is estimated that 90% of H&V control systems in buildings are inadequate. This costs industry and commerce £500 million per annum in additional energy costs."

Given that this was written some time ago the £500 million may be a little on the low side, but you get the point and indeed I hope see the opportunity, so I believe we have to ask two questions, first how come with all these sophisticated systems is the situation apparently as bad as it is and more importantly what can be done about it to take advantage of the apparent opportunity?

If getting the answer right is worth to the tune of £500 million per annum, as well as millions of tonnes of C02 emissions I believe it is worth addressing.

Before doing so however a bit of clarification is required. In reality, and I speak from experience, there is usually little or nothing wrong with the control system per se, the issues lie in how they are set up to manage energy. I feel therefore that the quote above guides us to look for the answer in the wrong place; the good news is that the solution is both relatively straightforward and shouldn’t cost a fortune.

First it is worth asking what is a BEMS supposed to do? There are many possible answers and among them one of the more honest might be “I don’t know!” It is a sad truth that most people charged with operating buildings and their control systems are inadequately trained to do so, therefore have little hope of delivering what the system should and in most cases is capable of, part of this problem lies in the complexity of the controls interface, indeed some systems are too complex for anyone with less than a PHD standard education to understand. I exadurate to make the point, but if the control interfaces for systems were simplified and standardised for day to day operation I am sure that greater energy efficiency and less time wasting (manpower efficiency) would result.

Secondly systems are primarily set up to ensure adequate building services are delivered, temperature set points, domestic hot water provision etc, and not for energy efficiency. This shouldn’t be the case because these two objectives are not mutually exclusive. After all the point of making a significant investment in a BEMS must be for it to deliver value. Quite simply a BEMS installed and set up correctly is capable of identifying what the demand for heating (or chilling) is and thus ensuring that only that demand is met. A couple of quick pointers; the greater the outside air temperature the less space heating is required and only run as many boilers as necessary to meet demand. I could go on, but you get the point. How many operators would be able to prove that their systems adhered to these simple rules? Not many and I think that they should and I also think that they would want to know.

Are there sufficient inputs and outputs (IO) to the BEMS to gain good control over primary plant? Here the issue is more has the BEMS infrastructure been set up to ensure optimal energy efficiency. Think about it, energy is actually being consumed in the boilers and chillers, from there it is merely being transported (as heating or chilling) to its point of use at marginal additional energy cost, the greatest opportunity for savings is therefore to ensure that only as much energy as is necessary is being used at point of consumption. So how good is the control over primary plant? There are thousands of plant rooms where individual boilers are not connected to the BEMS as a result they can not be being controlled to optimal efficiency. Likewise there are thousands of chillers running on their own packaged controls with no reference to what the heating is doing. Quite simply a case of the right hand not knowing what the left is doing and there should therefore be no surprise to learn that for much of the time they are both operating at the same time, hardly a recipe for efficiency!

Is the BEMS connected to the energy meters? Gas and electricity are the core energy that most BEMS manage, it is much more difficult to manage if they are not being measured on a regular basis, there is a vast amount of regular analysis that most BEMS are able to undertake to help in good energy management at a site, it is just a question of having them set up to do so. Find out what your system do for you and make sure that it delivers.

And finally (for the moment) there is the old axiom “If it isn’t broke…” here in lies one of the greatest problems and it is largely one of perception; energy performance in buildings is not a simple question of right or wrong it is more complex than that, rather look at it as better or worse, where 100% particularly sustained over any length of time is a utopian ideal something anyone managing a building should strive towards. In reality so long as the right temperatures are delivered no one really cares how much it is costing. However if an energy manager’s role is to do just that and ensure that only enough energy is being consumed to meet the building’s requirements thus optimising plant performance as well as the energy budget, the BEMS is the key tool for delivering these objectives.

What is getting it right actually worth? I have quoted a figure of £500 million, but to an extent this is not really meaningful to individual building owners or operators, so let me put this another way, from experience there are very few buildings where at least 20% of the energy for heating, ventilation and cooling could not be saved with a pay back inside 18-24 months. I think that most financial directors would look favourably on an energy management team that delivered a return like that. As someone once said; “if you reach for the stars you might just touch the moon”.