Thanks to Dave Covell of Clearlead Consulting for this picture of a magnet on a gas line which had grabbed hold of his steel-capped safety shoe as he was passing. We know magnets are useless, but it’s a bit rich that they make safety shoes hazardous…
John Cantor started out manufacturing and installing bespoke heat-pump systems during 1980s and 90s. He was system inspector for the first UK grants through BRE and was also on the MCS working group. He’s an honorary member of the Ground Source Heat Pump Association and author of ‘Heat Pumps for the Home’.
As well as heat pumps we’ll examine the realities of biomass installations and consider the prospects for hydrogen. More details at https://vesma.com/z200
Delighted to have Jan Rosenow opening our afternoon conference “Decarbonising heating – practical realities” on 8 July. Focussing on the non-domestic market, our speakers will discuss real-life experience with biomass boilers and heat-pump systems, and draw lessons for future projects. We’ll also hear from an expert on hydrogen about how that might be introduced into the national heating-fuel mix, and we have allowed plenty of time for questions from the audience.
Full details are at https://vesma.com/z200
WHEN thinking about possible energy-saving projects, you might ask yourself how radical you want them to be. There’s a spectrum from the relatively easy to the costly and disruptive. Readers may have their own views on this but I think the spectrum runs like this:
Effective energy waste avoidance relies crucially on the comparison of actual and ‘expected’ consumptions. Classically we do this on a weekly or monthly basis, using models for expected consumption that are linked to independent driving factors. But there are other ways to skin that cat.
Buildings will in many cases have a characteristic diurnal pattern of demand that can be expressed as a profile at, say, half-hourly intervals. With a large enough group of similar buildings, and taking account of drivers like the weather, it seems possible in theory to create a dynamic template for each building against which its demand can be assessed in near-real-time. The template is just a different way of calculating and expressing expected consumption, but it creates the realistic prospect of daily exception reports. Of course the implied excess costs need to be taken into account, because you need to be able to suppress the clutter of insignificant deviations, prioritise cases for investigation and estimate the value of resolving them, just as you would if you were using a weekly or monthly overspend league table.
The role of artificial intelligence here is to learn what ‘correct’ behaviour looks like and one advantage of this in large estates is that it obviates the need for human analysts to calibrate degree-day regression models for every meter. Another benefit would be the recognition of common abnormalities in profiles. Properly trained with correct human feedback, an AI-based pattern recognition system could in principle recognise symptoms that have occurred before elsewhere and associate them with remedies that have previously been successfully applied.
A further benefit is advanced benchmarking. In classical M&T we know that buildings can be benchmarked by comparing the slopes and intercepts respectively of their degree-day regression lines. A pattern-analysis system can take this more incisive analysis to a whole new level.
I will be interviewing James Ferguson, a keen proponent of AI in energy waste detection, on 15 July 2021 in my “Energy Conversations” series of open video calls. If this is a subject which interests you you can request a place in the audience here.
Reader Chris B. had seen someone promoting a product that could be retrofitted to passenger lifts to recover kinetic energy rather than dissipating it in friction brakes. He wrote to ask if it was a plausible offering.
Certainly there are lift systems that use regenerative braking, that is, motors which turn into generators when switched into reverse to decelerate the descending car. It is a legitimate idea, but usually a feature designed into the installation at the outset. As such it offers other advantages such as reduced heat dissipation in machine rooms. But it’s hard to believe that it would be viable to retrofit an existing installation because the available energy is not as much as you might think, as you can see from this rough calculation making some very optimistic assumptions.
Suppose a lift drops 36 m vertically carrying an excess mass equivalent to ten 80-kg passengers. As gravitational field strength is about 9.8 N/kg its change in potential energy would be 36 x 10 x 80 x 9.8 = 282,240 joule. That’s 282,240 / (3,600 x 1,000) = 0.0784 kWh. If you could harvest all that energy it would be worth approximately one penny. Factor in some more conservative assumptions and realistic conversion efficiency, and the value of the recovered energy is totally negligible.
Why are worthless bolt-on products like this promoted? In the case of products supposedly under development, it is usually to lure naive investors. For readily-available and easily-deployed products like bogus boiler additives and fuel-line magnets, it is to lure naive franchisees.
Learn about energy-saving techniques that actually work at this tutorial: “Energy efficiency A to Z” on 26-27 May
IN MARCH AND APRIL this year several national newspapers, including the normally sober Economist, carried articles promoting the concept of a microwave central heating boiler which could be fitted in place of a gas-fired one. The same story appeared in H&V News, a trade journal.
The originators’ objective is to promote the idea of decarbonising your heating by substituting (renewable) electricity for gas. The articles compare two options: electrifying your existing central heating system versus installing a heat pump. The latter, quite reasonably, they consider costly and not always feasible. But somewhat disingenuously they fail to mention another electrification option which I’ll come back to at the end.
Now suppose for some reason you did want your radiators fed by an electric central boiler. Why opt for the complexity of a microwave one rather than one based on simple resistive immersion heaters? It makes no sense because either way you can only get as much heat out as you put electrical energy in. Microwave sources confer no thermodynamic advantages. The promoters justify the more complex technology because (according to the account published in the Economist) immersion heaters “…must run continuously to deliver water at a suitable temperature. That often warms water which is never used.” Well, er, no. Immersion heaters would be thermostatically controlled, and wouldn’t consume energy that is never delivered as output heat.
Event alert: “Decarbonising heat: practical realities” on 8 July. Details at https://vesma.com/z200
In the version of the story on the Guardian web site, the company claims that the electrical load “will be about the same as an electric oven”. This also makes no sense. A built-in electric oven might be rated at 3 kW while a central heating boiler could quite typically have an output of around 30 kW and an electric version would need input power to match. Indeed according to the piece in H&V News these microwave boilers can be up to 60 kW in capacity. And therein lies a problem. Even a 30 kW appliance would need a 120-amp mains supply at 250V, and that’s on the assumption that it is a simple resistive load. To put that in context, our whole house is fed through a 100-amp supply. Microwave units, however, have notoriously poor power factor so will inevitably draw much more than 120A for the same 30kW duty, all of which makes claims of quick and easy installation ring somewhat hollow.
The coverage in H&V News is rich in whizzy-sounding technology and buzzwords. For example it says that the heart of the system is termed a “technology stack”, which they say is a “solid-state, robust RF framework that uses configurable and controllable high performance amplifiers to generate energy”. Elevating the merely meaningless to Olympian heights of drivel. The version of their story in the Economist includes the bizarre assertion that “the pipes that carry the water are also made of microwave-sensitive materials, as is the insulation that lags them”. Microwave-sensitive? Wait… like lasagne? And if the pipes heat up under microwave radiation what’s the benefit of the insulation doing likewise?
The article in H&V News quotes a director of the company claiming that their electric boiler “would cost the same to run as a gas boiler”. At least the Guardian had the wit to expunge that remark from the on-line version of the article. The truth is, if you want to use electricity for heating and a heat pump is not an option, individual room heaters would be the obvious way to go. Apart from being cheaper to fit than a new electric boiler, they would enjoy the advantage of room-by-room controllability.
Good morning
FEATURED EVENT: BUILDING INSULATION
This two-hour technical briefing on 19 May covers the materials and techniques currently specified for improving the thermal performance of buildings. It includes revision of basic principles, discussion of the limitations of each type of product, and a summary of relevant UK regulations and standards. Details are at https://vesma.com/z112 and as ever your readers’ discount code is EMR2012.
Other forthcoming events are listed at http://vesma.com/training.
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U IS FOR UNCERTAINTY
When we plot energy consumption against driving-factor values on a scatter diagram, the points don’t fall exactly on the regression line. The degree of dispersion is described by a parameter called the ‘coefficient of determination’, commonly known as R-squared, which tells us how much of the variation in energy consumption is explained by the regression model. When all the points fall exactly on the line, the model explains all the variation in energy consumption and R-squared has a value of one. If there is no relationship between consumption and the chosen driving factor, R-squared would be zero. If R-squared is 0.9 it means that the model explains 90% of the observed variation in energy consumption with the remaining 10% being attributable to errors or factors that were not taken into account.
There are two common misconceptions about R-squared. One is that on a heating system, a low value of R-squared signifies poor control. This is not necessarily the case, as the following thought experiment will show. Consider a well-controlled heating system whose consumption is assessed against a reliable local source of degree-day data. Whatever value of R-squared is observed, if you were to substitute degree-day statistics from a more distant weather station in the regression analysis, R-squared would go down, even though the heating system continues to be well-controlled. So beware: low R-squared might be telling you more about the quality of the model and your data than about the behaviour of the thing you are monitoring.
The other common misconception is that there is a threshold for R-squared (0.75, or 0.9, or whatever) below which your regression model cannot be trusted. There is no such cut-off. If you have chosen the most relevant driving factor and a straight-line model is plausible, you have got the right model and a low R-squared value just means it is not as reliable as it could be. In practice that simply means that a deviation has to be bigger before it can be treated as something that didn’t happen by chance. By refining the model you will improve your ability to discriminate between real faults and random variation. So it’s not a question of do you trust the model or not; the question is: “given a plausible model, how much uncertainty is there in its predictions?”. Hence the idea, introduced in an earlier bulletin, of tuneable +/- control limits on charts showing the history of deviation from expected consumption.
In the next issue: V is for verification of savings. Meanwhile if you missed any earlier issues you can catch up at http://EnManReg.org/azmt
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MAVCON 21: CALL FOR PAPERS
We’ll be running our measurement and verification conference again as a series on Wednesday afternoons starting on 20 October. By popular request the first two sessions will be a refresher on basic principles and good practice, and the final sessions will be aimed at advanced practitioners but open to all. If you have an idea for a presentation (even if you don’t want to do it yourself) please let me know now.
Kind regards
Vilnis
Updated 30/4/21 and 4//4/22
“Streamlined energy and carbon reporting” (SECR) is the term commonly used to describe the regime introduced with the Companies (Directors’ Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018, Statutory Instrument 1155. This is not a self-contained set of regulations like ESOS; instead it consists of nothing but dozens of amendments to existing company reporting law. In short, undertakings covered by SECR simply need to collate annual total energy and emissions data and give them to their company secretary or accountant for inclusion in the annual report that they already have to prepare.
As this is an extension of financial reporting, compliance will be policed by the Financial Reporting Council, and not, as one might have thought, by the Environment Agency. The good news is that in terms of accuracy and completeness, your SECR reports need only be free of material misstatements, and according to the Government’s published guidance it is fine for a company to omit 2-5% of its energy or emissions if it considers them not to be material in the grand scheme of things.
SECR applies to all quoted companies, and to unquoted companies and limited liability partnerships (LLP) which meet two of the following three criteria:
This is not quite the same as the ESOS regulations, in which an undertaking would be obliged to participate if it met criterion (1) alone.
Undertakings which consumed less than 40,000 kWh in the year being reported do not have to report their actual figures but must still state that they fell below that threshold.
It is fine for a company to omit 2-5% of its energy or emissions if it considers them not to be material
Group reports should include the figures for all subsidiaries apart from those that would be exempt. Under these circumstances a subsidiary need not report its own figures although, of course, it will still need to collate the data for group use.
The requirement covers energy use and greenhouse gas emissions arising from all use of electricity, gas, and transport fuels. Incidentally the definition of “gas” is not limited to natural gas, but refers to any gaseous fuel so it even includes hydrogen. The inclusion of electricity on an equal footing with other energy sources means that SECR differs from emissions reporting, in which fuels and pirchased electricity are considered under different ‘scopes’. Somewhat bizarrely liquid and solid fuels do not have to be accounted for, unlike in CRC (which SECR supposedly replaces) ESOS and EUETS. Bought-in heat, steam and cooling are included but not compressed air.
Quoted companies must report global figures, but LLPs and unquoted companies only have to declare UK consumption and emissions.
In the main, therefore, any undertaking that already keeps even very basic monthly fuel and electricity consumption records for its fixed assets will have no trouble collating the necessary energy data. Transport fuel, of course, is a different issue. As many an ESOS participant has found, transport fuel data are disproportionately hard to collect relative to its importance in the mix. Luckily, if you can reasonably assert that your transport energy and emissions are not material to the overall picture, you can just leave them out.
My advice would therefore be to look first at transport fuels, decide whether they are material, and if so put resources into capturing the data or estimating the figures.
SECR requires emissions to be reported as well as energy consumptions. The necessary factors are published by the government and undertakings would be well advised to set up a methodical procedure for carrying out the calculations, because they must include details of their methodology alongside the data that they report.
Undertakings must report intensity metrics, of which an example would be kWh per unit of saleable product output. The idea is that stakeholders will be able to see, once a year, what progress the company is making in energy efficiency. This is actually a somewhat naïve and fanciful aim, given all the ways that such simple ratios can be distorted by external factors nothing to do with energy performance. Even more implausible is the idea of making ‘benchmarking’ comparisons between enterprises, but that is the government’s stated objective.
Companies are entitled not to report intensity metrics if, in their opinion, it would be prejudicial to their interests to do so. For example it might entail disclosing sensitive information about their sales volume. One option is to quote a metric based on financial turnover (which is already disclosed anyway). This may not be meaningful, but then neither is anything else they might report.
Finally, annual reports must now include descriptions of the principal measures taken to improve energy efficiency during the year in question, if there were any.
Energy, emissions, intensity metrics and associated methodologies must be stated in annual reports covering accounting years starting in April 2019 or later, so by now all companies will have had full reporting years covered by the scheme (the last wave was for reporting years ending in February 2021). Actual report submission deadlines fall six months later for public companies, nine for private companies.
Good morning
FEATURED EVENT
We’re hearing a lot in the news, including ambitious government announcements, about ‘decarbonising heat’. Most of the media coverage is about the domestic sector but the chances are that, as a reader, your focus is more on commercial, public-sector or industrial buildings or larger-scale residential facilities. You may have heard that experience with biomass and heat-pump installations has not always been positive, and you will want to understand the problems and pitfalls. You may also be getting questions about how hydrogen in the public supply might play out, and need ready answers.
We’ve therefore arranged a half-day intensive workshop on the practical realities of decarbonising heat in non-domestic buildings, with a team of experienced experts to talk about the lessons that have been learned and the technical and other issues that organisations face in coming decades. Details are at https://vesma.com/z200 and as ever your readers’ discount code is EMR2012.
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T IS FOR TARGETS
In energy management the word ‘target’ has two distinct meanings. The first is the ‘aspirational’ target, usually set from on high without regard to practicability, to reduce consumption by x% within a certain time. It’s not a particularly smart approach. In fact in a large organisation it is almost guaranteed to fail, and here’s why. Top management sets a reduction target of x%. There being no easy, transparent and equitable way to do anything else, all departments adopt the same x% target and pass it down the chain to the lowest-tier managers. For some of them, x% is impossible to achieve so they fail. For others it will be achievable or even easy. They will save x% and then probably stop trying. Why would they over-achieve? They have other work to worry about and anyway we all know if we beat our target our managers will just give us a harder target next time. So take the roughly x% saved by the successful ones, blend this with the lower savings achieved by the first group, and you have an aggregate failure.
For me, achievability is key, and when I talk about a performance ‘target’ I mean just maintaining the best performance you can demonstrably achieve. In other words, avoid accidental excess consumption (see next article). This may not be ambitious but it is worth doing; using regression or other modelling methods supported by cusum analysis it is possible to ensure that everything has its own achievable performance characteristic. The word ‘achievable’ is crucial: it’s much more likely to get buy-in than the megaphone-management targeting that I described earlier.
I said achievable ‘characteristic’ because my concept of a target differs from common understanding in another important respect. My ‘target’ is not expressed as an annual kWh figure, nor indeed as a performance indicator, but in terms of an expected consumption quantity dynamically linked to relevant driving factors, meaning that you can track performance at whatever interval you want.
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£50 FOR THE CHARITY OF YOUR CHOICE?
If you’ve ever stumbled over something that was wasting energy in a manner that was easily avoidable, I’d like to hear about it. Every month we’ll donate £50 (or the equivalent) to the charity nominated by the person whose entry is deemed the best by our guest judge. Details at http://EnManReg.org/starspot
Kind regards
Vilnis