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Accounting for the weather: an early degree-day meter

ddmeter1

I’m indebted to Dr Peter Harris for unearthing this curiosity, published in the journal of the Institute of Heating and Ventilating Engineers in 1936. It is a design for a “degree-day meter” whose purpose was to summarise how cold the weather had been over a given period (a month, say). This is how it works: a resistance thermometer a is mounted outdoors and connected via a Wheatstone Bridge b to a moving coil galvanometer c whose pointer d moves horizontally across a scale e, marked from 60°F on the left to -20°F on the right. It thereby indicates the outside air temperature. Above the pointer is a tapered chopper bar f, moved up and down by a light spring g driven by a rotating cam h.  Because the chopper bar is tapered, its vertical travel is constrained to an increasing extent as the pointer moves leftward indicating higher temperatures.  Conversely, its vertical travel will be greater the lower the temperature, as the pointer moves to the right. The intermittent vertical travel of the chopper bar is transmitted via a pawl i and ratchet-wheel j to a cyclometer counter k which shows the total vertical travel. The counter will advance more rapidly when it is colder and more slowly when it is warmer outside, and it is so arranged that when the temperature exceeds 60°F there will be no vertical play and the counter will not advance at all.

Because a building’s heating power requirement at any given moment is proportional to the temperature deficit, the accumulated deficit over any given period of days (as measured by this meter) is proportional to the total thermal energy lost from the building, which needs to be made up by the heating system.  Because it measures the time integral of temperature deficit, its units of measurement are degree-days (analogous to man-hours) and the threshold temperature of  60°F survives today as the common degree-day base temperature of  15.5°C.

A little light reading

Got your shopping basket and cheque-book ready? Let’s build that library of energy-management systems standards!

We’ll start with ISO 50001 “Energy management systems. Requirements with guidance for use” at £174 (or bizzarely, £12 less for the laminated version), and to make sure we implement it correctly, fork out £212 for ISO 50004 “Energy management systems. Guidance for the implementation, maintenance and improvement of an energy management system”. To help us understand it all we might add PD CEN/CLC TR 16103 “Energy management and energy efficiency. Glossary of terms”. That’s only an extra £152 but we can probably pass up on ISO 9229 “Thermal insulation. Vocabulary” (£200) especially as the subject seems also to be covered in the cheaper ISO 9251  “Thermal insulation. Heat transfer. Conditions and properties of materials. Vocabulary” at just £90.

Stay with me… Next, we will almost certainly want to do some energy audits. ISO 50002:2014 ED1 “Energy audits. Requirements with guidance for use” would seem to cover the ground, and at £103 it’s £5 less than the European Standard EN 16247-1 “Energy audits. General requirements”. But – decisions, decisions – EN 16247 also boasts other sub-standards: Part 2 for buildings at £192; Part 3, processes at £146; and Part 4, transport at £104 (the prices differ because they charge per page). If we want to use benchmarking we could pick up a copy of EN 16231 “Energy efficiency benchmarking methodology” for only £152, and thinking about the qualifications of the people doing the work we should add PAS 51215 “Energy efficiency assessment. Competence of a lead energy assessor. Specification”, which at £70 seems quite good value until you read it.

Swap your shopping basket for a trolley now, because we’re going to think about measuring and verifying our savings. To set the scene, let’s fork out £212 on EN 16212 “Energy Efficiency and Savings Calculation, Top-down and Bottom-up Methods”. Please suppress the thought that probably crept into your mind on seeing the words “up” and “bottom” in the title of one of these worthy publications, especially as we will see them again when we splash out £146 on CWA 15693 “Saving lifetimes of energy efficiency improvement measures in bottom-up calculations”.  Then to be on the safe side let’s get ISO 50015 “Energy management systems. Measurement and verification of energy performance of organizations. General principles and guidance” at £152, plus ISO 50006 “Energy management systems. Measuring energy performance using energy baselines and energy performance indicators. General principles and guidance”  (£174). Nearly done… To make sure that our efforts to comply with all this stuff are up to scratch, let’s round off with £146 for ISO 50003 “Energy management systems. Requirements for bodies providing audit and certification of energy management systems”.

All in all, the bill could be over £2,000. There is no truth in the rumour that the International Standards Organisation, British Standards, and the Comité Européen de Normalisation are contemplating a joint venture to be called “ISO, BS and CEN Enterprises” or ISOBSCENE.

Choosing an assessment interval

By default, I tend to favour a weekly assessment interval for routine exception reporting and associated analysis. Monthly is too long for all except the smallest users (although it may be appropriate for passive top-management reports for users of all sizes) and months are also too inconsistent in terms both both of duration and number of working days.

In some applications, daily analysis may be viable, for example:

  • in buildings such as data centres which operate seven days a week and respond rapidly to changing weather conditions; or
  • in energy-intensive manufacturing processes.

More frequent near-real-time assessment is sometimes attempted but this brings complications that tend to outweigh the benefits. Firstly, there will be error induced by short-term effects such as transients, lags, latencies, and factors which are not practical to take into account but whose random influences would have cancelled out over a longer time interval. Secondly, the cash values of excess consumptions over a short interval are very small. Thus with too-frequent reporting the user is continually bombarded with trivial alerts which often prove fleeting. Not the best recipe for engagement.

Having said that, where fine-grained data are being collected they can be an invaluable diagnostic aid; but the best reporting tactic is to review performance at, say, a daily or weekly interval and use the real-time record for diagnosis by exception.

 

 

How to waste energy No. 9: energy audits

For the keen energy waster faced with demands to have an energy audit, it is vital to employ an incompetent assessor — one who can be expected to follow these principles:

1. Just turn up at site with a clipboard and start counting light fittings.

2. Never analyse historical data to identify anomalies that you could productively focus on during site visits.

3. Base your report on a previous one for a different client. A good trick is to use ‘find and replace’ to change the name in the body of the text, but overlook where it appears in headers and footers.

4. Always make at least ten recommendations, even if there is only one substantial worthwhile measure.

5. Always include recommendations for LED lighting and voltage reduction.

6. Over-estimate the savings expected from each recommendation.

7. Ignore any possibility of interactions between recommended measures.

8. Never obtain actual installation costs. Reverse-engineer them: take the annual savings and multiply by an assumed payback period.

Of course as a client, the keen energy waster has their own part to play in making the audit a futile exercise. Here are some tips:

1. Do not let anybody in the organization know about the audit visit.

2. Render all relevant data and drawings inaccessible.

3. When you receive the report, ignore it.

How to waste energy No. 8: road transport

Transport in all its forms provides excellent opportunities to waste energy. Here are a few related to car, van and truck use:

1. Never arrange a telephone call or video conference if you can drive to a meeting instead. Driving long hours shows you are working hard.

2. Never share a car journey.

3. Make sure drivers have not got clear directions to their destinations, so that they get lost.

4. Use oversized goods vehicles whenever possible, and avoid consolidating loads to improve load factor.

5. Do not plan freight movements. For example if back-loads are available, it is better to send out empty vehicles to fetch them.

6. Never optimize multi-drop delivery routes.

7. Never give drivers training. Encourage them to accelerate hard, drive too fast in too low a gear, brake harshly, and idle their engines for long periods.

8. Fit the wrong kinds of tyres and run them at the wrong pressures.

9. Neglect maintenance of tracking and brakes: as well as wasting fuel you can spend extra on tyres and brake parts.

10. Do not monitor mileages, loadings or fuel purchases.

How to waste energy No. 7: meter reading

A big part of wasting energy is not knowing how much you use, when, where or for what. Most keen energy wasters rely on their energy suppliers not read their meters for them, but here are some top tips for those who want to be proactively bad:

1. Make it difficult to get access, for example by installing meters at height, or leaving the keys to the meter room with an obnoxious jobsworth.

2. Try to have meters installed in positions where you cannot see their dials.

3. Never have a reliable check-reading taken by somebody who knows what they are doing.

4. Do not create a meter schedule; if you have one, don’t keep it up to date.

5. Do not try to find out what each meter serves.

6. If in doubt about units of measurement or scale multiplier factors, make whatever assumptions you like.

7. When a meter is swapped out, dispose of the old one without noting its final reading.

8. Do not train anybody to read meters.

9. Do not appoint stand-ins to cover for sickness or holiday absence.

10. Allow meter readers to be lax about when they take readings, and let them record the date they were supposed to take the readings rather than the actual date and time.

11. Allow meter readers to include or ignore decimal fractions as they feel inclined, if possible being inconsistent between visits to the same meter.

12. Rely on paper returns, and lose them.

Link: Energy management training

 

How to waste energy No. 6: air conditioning

The hot weather brings with it demands for air conditioning, and with that comes a whole raft of excellent ways for organizations to waste energy. Here are my top ten hot tips:

1. Don’t argue when people ask for rooms to be cooled to 20C rather than the more sensible 27C. Every degree reduction in set-point adds 10-15% to the electricity used for cooling, and you may even hit the jackpot of some people turning on electric heaters as well.

2. Encourage people to leave the windows open with the air-conditioning on. This allows warm air in and expensively-cooled air out, more or less guaranteeing that the air conditioning will have to run flat out without reaching the desired internal temperature.

3. If it is not possible to leave the windows or doors open, minimise the recirculation of ventilation air.

4. Do not take advantage of lower overnight outdoor temperatures to pre-cool occupied spaces.

5. Encourage people to leave idle electrical items running, to increase the heat gains. Desk fans are an excellent example for those who can appreciate the irony: by creating air movement they make the occupants feel more comfortable, while continuously heating the air a little.

6. Believe your IT department and equipment suppliers when they say their kit needs to be housed at 16C (the idea that it might be designed to operate in tropical climates is ridiculous).

7. In computer rooms have the equipment racks all in the same space, so that their warm extract air mixes with the chilled air needed for intakes. Under no circumstances partition the space to separate cold and warm air.

8. If possible, house people and equipment racks in the same space as if they needed and/or could tolerate the same conditions.

9. Do not shield windows from direct sunlight.

10. Always use artificial cooling when increasing the ambient fresh air supply would do the job equally well.

Energy management training

Struggling to verify savings?

When people ask me for advice on how to verify energy savings, it is usually because their analysis is not giving the results they expected. Often they have left it too late, developing a methodology after the event or even making it up as they go along. So if you are contemplating an energy-saving project the first plea I would make is this: agree a measurement and verification plan between the interested parties before the project starts. That way, everyone is forced to think about the calculation methodology and (just as importantly) focus on what data will be needed, who will collect it, and even how much uncertainty there is likely to be in the conclusions. It also pays to think about what non-routine changes might occur (patterns of occupation, extensions, demolitions, etc) and agree how those will be factored in if they occur.

Sometimes, fortunately, it is possible to rescue the verification of a project where the “shoot first, ask questions later” approach has been used. To achieve a resolution one needs two things: first a willingness on both sides to accept a retrospective definition of procedure; and secondly, at least some accurate prior consumption data. That consumption data can, however, be sparse, so the presence of a lot of estimates (a common situation) need not necessarily be a problem. The analysis in such circumstances is done using a technique called “back-casting”.

Recall that in a normal evaluation, accurate and complete pre-project baseline data are needed so as to establish the prior relationship between consumption and relevant independent driving factors (such as degree days, hours of darkness, production and so on). A formula is derived, typically using regression analysis, for predicting consumption from those driving factors. After the energy conservation measure (ECM) has been installed, that same baseline formula can be fed with driving-factor data and will yield an estimate of what consumption would have been in the absence of the ECM. The spread between this estimate and actual consumption is a measure of the ‘avoided’ energy consumption.

The back-casting method is different. It turns that logic on its head. Using post-ECM rather than pre-ECM measurements, a formula is developed which relates consumption to driving factors for the improved installation (rather than its original performance). Thus you can say that the analysis “baseline” period follows, rather than precedes, the ECM, which some people find odd. In this scenario, pre-ECM actual consumptions can be compared with what they would have been if the ECM had been active all along, and one would expect those actual consumptions to be higher than the model’s predictions (the opposite of the conventional approach where post-ECM consumptions turn out lower than the baseline model predicts).

Back-casting is no less valid as a method, but it enjoys one big advantage in that you only need two firm meter readings predating the ECM. They should be as far apart in time as possible, and you need to be able to retrieve driving-factor data spanning exactly the entire period between the meter readings, but if those conditions are met, your model formula can tell you what the expected consumption of the installation would have been over that entire period if the ECM had already been in place, and hence how much more was actually used in the absence of the ECM. This back-to-front approach is attractive because regular meter readings are generally easier to assure after the project than before.

Link: Energy management training

How to waste energy No. 5: motivation and awareness

People are your greatest asset in the battle against energy efficiency. Here are my top tips for disengaging your workforce:

1. Focus on trivial behaviours like leaving phone chargers plugged in.

2. Position climate change as a key consideration in order to maximise time-wasting and unproductive debate. Remember also that a message of fear will paralyse rather than stimulate action.

3. Over-promise with slogans like “together we can save the planet”.

4. Give away branded mugs, coasters and other merchandise to enrage anyone bothered by waste of resources.

5. Do not canvass people for their opinions or ideas: remember the best instrument of communication is a megaphone.

6. If you do an opinion survey, use on-line techniques to be certain of reaching only those with computer access.

7. Use multiple-choice questions to be sure of missing responses you did not expect (obvious missing options also infuriate and alienate people).

8. Mount a high-profile launch event before you are ready with follow-on activities.

9. Appoint energy champions and leave them to sink or swim.

10. Be slow responding to staff suggestions.

11. If a suggestion does win an award, do not implement it.

12. Give individual cash awards: they can be wonderfully divisive if they are perceived as having gone to an undeserving winner.

13. If payouts are a share of savings, be ready to reduce the share for really successful ideas.

14. Don’t forget everybody loves to be awarded a T-shirt with an energy-saving slogan on it.

15. Have a poster campaign.

Link: Energy management training