Friday, August 24, 2007

Amazing Irish Heating Efficiency Claim


Amazing Irish Claim
Super Super Super Efficient
Electrical Heating

Yet again, my West Cork alternative energy expert has pointed me towards a very interesting claim being made by an Irish alternative energy company.

This company, among its other products, are offering an under-floor electric heating system which it claims uses only 3.5 Kw and no more than €500 euros worth of power in an average year for an average sized Irish house.


If this is true for the average home - this is really extraordinary and deserves publicity. Somehow I have serious doubts about the level of the claim.

I did a rough heating loss calculation for an bog average 3 bed house with a moderate level of insulation, and my estimate is that it would take at least 3 times the electricity being claimed to adequately heat the house to say 21 degrees.

Questions Immediately Spring to Mind:

1. How does a mere 3.5Kw heat an average home in mid winter with say minus 2 degrees and wind outside?
2. How do they justify an annual running cost of €500 = 3571 Units at their figure of .14c KWh. That's an average of just 1000 hours in the full year of electricity - or just 3 hours per day.

Anyone in the heating business will know the following rough formula for calculating heat requirement:

1 kW of heating output will approximately heat:

25 cubic meters of a well insulated room.
15 cubic meters of an average insulated room.
10 cubic meters of a poorly insulated room.

An average living room might be say 12' x18' x8'.
This approximately equals 50 cubic meters.
To heat 50 cubic meters properly in a well insulated room it would need 2Kw.

That would leave only 1.5 Kw to heat the rest of the house according to this claim!!!

Intrigued but Doubtful.

I am really intrigued and wondering what have these guys stumbled upon, but, as I said, I have serious doubts about the scientific basis of their claim!!!

I have some engineering and heating background. I worked with Shell BP as a heating engineer many years ago. I therefore have a basic knowledge of heat loss, thermal efficiency, and heat requirements.

I also know from practical experience, living in flats without central heating, that 1Kw, a one bar electric fire, will not keep an average living room warm enough for much of the year even if it is run 24 hours a day - due simply to heat loss in the average house.

Even with 100% efficiency Watts to BTU’s conversion I cannot see or understand how this system can work- unless the system is running "Over Unity" or has some other source of energy such as "geothermal". 3.5Kw will simply not be enough to heat an average home on a winters day.

Awaiting Information.

I have made contact with this company and have had initial response. I will await further information before naming the company.

I would really love to know the scientific principle behind this heating method, along of course with some independent figures and measurements. The type of measurement of interest would be "Watts (Volts x Amps) in v/s BTUs" out. This would be an easy enough measurement to achieve. So if the heating elements can output higher BTUs than a basic heating wire - it would show up in the figures very quickly.

Underfloor systems cannot by their nature react to requirement very quickly due to thermal lag i.e. they have to heat the floor material first. Therefore no matter how efficient a control system is, if someone leaves the door open for a while, there is going to be a chilly room for a while. The thermostat will pick this up and will turn up the heating - but by the time the flooring materials heats and the floor material to air transfer of heat takes place - a good bit of time will have passed.

This underfloor system is essentially a storage system using the heat lag of the floor material. There are suggestion that an efficient control system is the basis of its success. I know from science and experience that no amount of control can substitute for heat quantity.

A one bar fire will not heat a big cold room on a freezing windy winters night - no matter how sophisticated the control system is!!!

Basic science!


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