Using the waste heat generated by domestic appliances?

Chris_Nowak

Does anyone know of any practical ways of using the heat which normally goes to waste from everyday household items?

It seems to me that there could be ways of harvesting and storing the output from items such as irons, kettles, toasters, ovens, fridge condensers and maybe even things like light bulbs.

Could the family car, back from its school run with a nice warm engine, also have a role here?

bryanb

Chris_Nowak wrote: »

Does anyone know of any practical ways of using the heat which normally goes to waste from everyday household items?

It seems to me that there could be ways of harvesting and storing the output from items such as irons, kettles, toasters, ovens, fridge condensers and maybe even things like light bulbs.

Could the family car, back from its school run with a nice warm engine, also have a role here?

Hard to think of a way to store this heat, but all except the car are already helping to warm the house, assuming you use them indoors. The item that actually wastes heat in our place is the tumble dryer exhausting to outside.

malc_b

Light bulbs are the classic example. Most low energy bulbs give the saving based on the waste heat going to waste yet most of the time a 100W bulb is cutting your heating need by 100W. In uk this year I'd say 11/12th of the year!

mech_2

malc_b wrote: »

Light bulbs are the classic example. Most low energy bulbs give the saving based on the waste heat going to waste yet most of the time a 100W bulb is cutting your heating need by 100W. In uk this year I'd say 11/12th of the year!

For me, even if I have the heating on every day from now until the end of the year, it would be 8.5 months this year. Let's call it 9 months, 75% of the year.

If you use electricity at daytime rates to heat your home, you would be right. The saving would be cancelled out when the heating is on, but not many people do that. Most people (85%) in this country heat with mains gas. The savings then get much more complicated.

Let's assume a 20 watt compact fluorescent bulb is equivalent to a 60 watt incandescent bulb. The saving from 60 watts to 20 is 67%. For 3 months of the year we assume the house doesn't need heating, so 25% of 67% is a saving straight away. That's 16.75%.

For the other 9 months of the year, the electricity turned into waste heat by the 60 watt bulb would help heat the house. Let's assume tier 2 gas costs 3.2p per unit and is burnt in a 65% efficient boiler. That means each kWh of useful heat energy from gas is really 4.92p owing to boiler inefficiency. Let's use an electricity cost of 11p per unit for comparison. 4.92p is about 44.7% of 11p, so it's 55.3% cheaper to heat the house with gas rather than the waste electricity. So 55.3% of our 67% electricity saving is an actual cost saving, making 37%.

So for the whole 12 months of the year it's 75% of 37% plus the 16.75% from earlier. A total saving of 44.5%.

Of course, with a more efficient boiler the saving is greater.