I have converted part of a detached garage into a office. The floor, ceiling and all the walls are well insulated and now I've come to the problem of choosing a heating source. Due the buildings location a rad from the CH in house is not possible and i don't want one of those portable gas bottle fires so i guess my only option is an electric heater. Has anyone tried one of those oil filled electric radiators? Are they expensive to run and is 2K powerful enough for a room 3m x 4.5m? Is there anything else on the market that is suitable?
Without knowing the thermal properties of the insulation, no one can say. Quick back of an envelope, you'll need 500W of heating to handle 2 air changes per hour, even if the insulation is 100% perfect, and more than this if you will want to do a fast warm up from a cold starting point.
In the summer, I fitted a B&Q air conditioner. I've been playing with its heating mode in last few days (although it hasn't really been cold enough). It gives out 3.8kW of heat for 1.3kW power consumption. If B&Q have any left, it wouldn't surprise me if they might start going cheap at this time of year. I don't know how well they might work if it gets cold enough to ice up the outdoor unit though -- it is doing something which might be a defrost cycle when it switches off, but I don't know for sure. It would give you air conditioning in the summer too, of course.
I have a portable Dimplex oil-filed electric radiator - its just like any other radiator when up to temperature. I have it for emergencies i.e. if the combi packs up, or if someone needs the spare room, which was never fitted with a wet radiator. It has its own thermostat so you can set the output.
Electricity is several times the cost of gas. Even though it is 100% efficient at being turned into heat in an heating appliance, gas is still up to 90% efficient with a condensing boiler so that doesn't equalise the difference. Unless you go for thermal storage on economy 7 then you will be paying out several times ( three or four IIRC - I stand to be corrected ) for electricity what you do for gas.
Your other option is an electric halogen radiant heater or an electric fan heater. A fan heater might have an advantage over a radiator in that it is up to speed in seconds and if situated right next to where you are sitting can get you warm in minutes. Ditto with a halogen heater, though that'll probably get you warm on one side only, unlees you get two!
Look at a heat pump air conditioner. Used as a heater you get about
2 or 3 times the heat output compared with the energy input. So for
3kW output you pay for 1 or 2 kW input. As a bonus you get an air conditioner for the summer.
Price about GBP300 if you hunt around eBay for a DIY fit.
Oil filled rads, cheap convection or electric fan are all suitable.
A lot depends on the way you intend to use it, but I personally like wall mounted fans up high that push hot air downwards. Like hot air 'curtains' in shops. these at least suck the hot air from up high and blow it to the floor where your tootsies are. Blowers also seem to get the place more evenly heated quicker
2-3KW is totally adequate if the insulation is good. On really icy days, plug in a 10 quid convector as well if necessary
Not so, because of the voltage drop between the meter and the appliance. Some heat will always be dissipated in the wiring - whether this counts as useful heat or waste heat depends on the particular circumstances. In the worst case, with 4% voltage drop the efficiency is only 96%.
And then of course efficiency wrt the primary energy source is generally very poor, maybe only 35% overall (40% generation * 90% transmission *
Our hydro and wind generation is negligable compared with coal/nuclear/gas. Our coal and nuclear plant are old and inefficient compared with modern ones. Our gas plant is newer, but was cheap and inefficient even compared with what was available at the time.
The original Q was about electrical generation. the UK's Thermal generation I would imagine is no more than 30% efficient. 50% efficiency is about the best that can be achieved with materials that are suitable for large scale use. The usual limiting factors are the yield stress of the boiler (steel) components, and the lowest ambient (assisted by evaporative cooling) temperatures. Unless materials that can withstand the pressures at higher temperatures can be invented we are limited in the efficiencies that can be accomplished for high output generation.
You'll almost certainly find it only uses 2.5kW during warm up, and soon cycles to much lower power, perhaps 500w. It also wont move the air round, so in all will make a crap room heater at a high price. Get yourself a fan heater.
Slightly above mid 30's would be the worst thermal generation in the UK, typical of 60's and 70's built coal and oil fired generation. Top end for these is about 38%.
High 40's to mid's 50's is typical of 1990's gas fired generation. Very recent gas fired generation is even higher, 60% for instance in the case of Baglan Bay.
You are not comparing like to like re Baglan Bay. This is a CGT system of limited capacity (500MW) I believe whereas the large steam turbine stations are 3000MW plus with efficiencies, as you say, in the upper 30s. I stick my neck out and say that steam turbine stations do not exceed 40% efficiency (latent heat and all that jazz!).
On Sat, 21 Oct 2006 22:33:55 +0100 someone who may be "Tom" wrote this:-
Are you thinking long term or short term?
Short term, if you have an off-peak electricity supply, a storage heater will be cheap to install and reasonable to run. Peak electricity is best avoided for heating.
Long term, the options people have mentioned all have attractions, though heat pumps running on peak electricity are rather more expensive than ones which charge up some heat storage. Gas and water can be run to the garage just like electricity, so extending the existing heating and a gas fire are all possible. Remember that if you run such services into the garage then you need to think about the earthing of the electrical supply.
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