Sunday, October 21, 2007

Energy saving advice

Dear Mr Brinkley. Thankyou for filling out our home energy check questionnaire: an important step towards using less energy to heat, light and power your home. Using the information you’ve provided, we’ve come up with a practical look at the energy you use and can save at home.

About a month previously I had responded to a questionnaire that had arrived, unsolicited, by mail from the Energy Savings Trust. It asked me lots of questions about my house and suggested that if I send it back to them they will supply me with a mini energy audit. Only I don’t think they called it that.

I was interested to know what they would say because our house is arguably an interesting case. Built in 1992, it was certainly someway in advance of building regulations at the time. In particular, it incorporated underfloor insulation (not mandatory until 2002) and low-e double glazing (back when low-e was cutting edge). The walls had a little extra insulation and the oil-fired boiler heating system was reasonably well designed and included zone control, as well as thermostatic and time switching. It’s a well-built house and it probably rated as a Best Practice for 1992 sort of house, but certainly not an eco house.

The question that I was interested to see answered was what the EST would suggest that I did to upgrade the house. In fact, they have only made one suggestion. That is that we upgrade the boiler to a condensing boiler for a saving of £85 a year. Or, in terms of CO2, 0.6 tonnes.

Funnily enough, we did consider installing a condensing boiler when we built the house. Back then, there was only one oil-fired condenser on the market, made by Geminox, a French manufacturer. Our green-tinged plumber, Norman Cox, was keen for us to fit one, but in the end I took the decision that it wasn’t worth paying the extra £1,000 or so required to fit — cash was tight back in 1992 and I had heard one or two stories about the early Geminoxes which didn’t inspire confidence.

We ended up with a Boulter Camray (now part of the Worcester Bosch group) which has been chugging away these past 15 years. It gets an annual service (cost around £60 plus parts) and it occasionally breaks down. The last time this happened, I enquired from Shelford Heating about replacing the boiler with a condenser but was told that not only would we have to bear the cost of a new boiler, but that the oil tank would have to move because the position we placed it in in 1992 (right next to the house wall) is now regarded as a fire hazard (Part J of the building regs having been “upgraded”). Not only would that double the expense but there is no obvious place in the steeply sloping garden to place a new oil tank. It would in fact represent a major piece of civil engineering. So a replacement boiler would probably end up costing us around £8,000. Hmm. Should have fitted the Geminox 15 years ago, shouldn’t I.

Anyway, I am slowly but surely getting around to the point of this post. The Energy Saving Trust gave us a C rating, based on what I told them. This is sort of similar to the rating we would be getting from an energy performance certificate. I have no quibbles with that: it was what I expected. But the point is that they only made the one suggestion for improvement, which was to replace the old boiler with something more efficient. The saving was actually pretty minimal. Either with or without a condensing boiler, our not very old house still uses a fuck of a lot of oil. Around 2500lts each year (that’s just over a tank full). That converts to just over 25,000kWh, which converts to 7 tonnes CO2 per annum. The Energy Savings Trust estimation is pretty accurate on the size of our oil bill (just about £1,000 with oil at 36p/lt) but grossly underestimates our CO2 footprint: they suggest just 4.1 tonnes of CO2 per annum. I reckon it is over 7 tonnes. Why should that be? Do they use different conversion factors to me? I’m on 0.265kg CO2/kWh, which is the “industry standard.”

So my poser for the day is what should happen to houses like ours? If it was built to Passivhaus standards, or Code Level 4, and was still heated using an oil-fired boiler, it would be burning about a third or even a quarter of this quantity of oil, releasing maybe just 1.5 tonnes of CO2 a year to get space heating and hot water. So, although our house is probably more energy efficient than 90% of the UK housing stock, it still performs miserably in terms of what could be done. But there appears to be no upgrade path apart from fitting a condensing boiler, which really only makes a marginal difference.

I don’t have an answer to this, but it does highlight the enormity of the problem. What exactly do you do to a house that already has cavities full of insulation and has 200mm of the stuff in the loft, but still eats energy like it’s going out of fashion?


Blogger Stephen said...

This blog was to be in the "Heat Pump" page but no more responses were accepted.

Having read through a few blogs, I consider it may be helpful to make some contribution within this forum as the comments read, whilst not many, are typical of those myths and legends that currently surround the industry.
Firstly, if you are to listen to me and consider if my views are worth accepting, then who am I?
My name is Stephen Thomas, Owner Manager of OGI Groundwater Specialists Ltd, based in Durham.
BSc, MSc from University of Wales, Swansea, joined environmental consultants in USA assessing geothermal projects in1980’s, then Doctorate from Oxford University, then started OGI in 1989.
Charted Civil Engineer & Water & Environmental Management, European Engineer.
Currently designing & installing ground source systems for commercial buildings to reduce carbon dioxide emissions.
The following is not aimed at offending anyone, just to educate, as it is my view that heat pumps are here to stay and that this country needs to accept this fact. We are not manufacturers but designers, pulling together the best aspects of GSHP’s, Underfloor Heating & Solar.
Point 1 – The responsibility of those writing articles
To Tim Pullen. RE: The Article “HEAT PUMPS: Do they really work?” (Which I read prior to the dentist chair). This article had some interesting & valid points. However, much of the information was sadly out of date. Furthermore, some information was simply wrong and will give a poor impression to the public. For example, the temperature at 1.2m below ground level is quoted as a fairly constant 70oC to 120oC, with air temperatures between 250oC and -20oC.
Average ground temperature in UK is between 10oC to 12oC. There must be a misprint by the printers. Yet, this is what the public read. It is important that the articles must be accurate otherwise the public will be confused.
Point 2 – Do heat pumps reduce CO2 emissions over natural gas or heating oil.
Point 3 – By how much do heat pumps reduce CO2 emissions
This is the key question and links in with the basic equation which incorporates CoP (Coefficient of Performance).
Energy to building = COP x Electrical energy used.
Electrical energy used (proportional to CO2 emission) = Energy to building/ COP.
So CoP is critical. IF CoP = 4, then 1 kW electricity produces 4 kW heat.
As 1 kW electricity produces twice the CO2 than 1 kW natural gas, then based on a CoP = 4, GSHP results in approximately half the CO2 emission than natural gas.
Point 4 – CoP
Consider CoP in the same way as mph for a car. Just in the same way that mph is dependent on factors such as speed, weight of vehicle, type of fuel, head wind, tail wind, type of driving (i.e. heavy acceleration), motorway of town driving, so CoP has similar factors:
(i) Temperature of fluid abstracted from ground
(ii) Amount and design of ground loops
(iii) Type of heating (UFH, Rads)
(iv) Type of occupancy (Industrial, residential, commercial, home)
(v) Efficiency of heat pump
(vi) Integration with other renewable, e.g. solar
(vii) Is DHW required?
We have installed systems that will provide a CoP up to 5 by advance heating the ground using an accelerated solar capture system. Note that CoP will increase by 4% for each degree above 0oC that the fluid enters the heat pump. So if you can engineer a system that ensures a fluid return at 10oC, then CoP is raised to 4.4 from 4.0.
Point 5 – The future
Rarely mentioned is the extraordinary level of control within a heat pump. From our experience, it is the electronic monitoring of the external and internal temperatures that can result is substantial savings, especially when linked with UFH.
Also of benefit is the passive cooling (note that active cooling, i.e. when the heat pump is used in reverse still uses electricity). Passive cooling simply circulates the liquid in the ground and removes the heat from the building (also accelerates heat recharge to the ground).
Note also that manufactures are continually improving heat pumps. CoP = 4.2 is now pretty standard. Furthermore, systems are designed to use the most efficient stages of the HP to the most effect, but allowing additional energy only when required.
It is true that the industry is growing, and it is encouraging to see a range of peripheral equipment being developed from all over the world.
As designers and installers ourselves, we work with main contractors and are required to work within the contractor’s health & safety plan to avoid risks to those installing. We are also required to warrant the system, including a substantial indemnity to ensure that the installed system meets the client’s requirements (including reduced CoP emission).

In conclusion, I repeat that Heat Pumps are now here to stay, with or without “Green Electricity”. I would recommend that those with influence, e.g. those that get their articles into a dentist waiting room, need to get their facts right first as these are more influential than my Method Statements, Risk Assessments or Differential Equations.
Dr Stephen Thomas
Technical Director
PS: I would welcome hearing from any person with a real or perceived concern or question regarding GSHP’s. As a company we do not do domestic installations, but we would consider developing a simple advice sheet for the public at large, and something that more influential authors can refer to.

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