Andy Champ wrote:
The Natural Philosopher wrote:

If you use a heat pump, electricity is actually cheaper than gas or
oil, just about. its certainly in thee area where a blanket statement
is not true. The devil is in the details.

secondly, the efficiency you get from a petrol or diesel generator is
far less than you get from a properly constructed power station, and
you will almost certainly end up paying road fuel tax on the fuel.
Even if you don't, its very marginal. And you cant get a domestic
nuclear reactor, which is of course currently pipping the post as the
cheapest way to push electrons down wires.

you probably only get 20% eff. form a diesel generator, and that
varies with the load. A good power station averages the load of lots
of people, and achieves up to 60%. AND they can forward buy fuel in bulk.


You can get 80% eff* off a boiler heating water. Maybe more.

Compare that with 60% for the power station and 95% for the grid. No
point in direct electrical heating carbon wise unless you use nukes to
make it.

Finally, if nuclear power becomes widely adopted, and fossil fuel
start to get hard to extract, and or attracts a carbon tax,
electricity will in time be cheaper than fossil fuel.

*true thermal efficiency, not concocted figures by boiler manufacturers.


Is a domestic scale CHP system feasible? (use the coolant and hot
exhaust from your diesel to heat the hot water / radiators)


Of course its feasible: whether its cost effective is quite another matter.

Its a bloody poor way to make watts in summer!

at 20% efficiency a 25bhp engine (small 2 liter non turbo diesel at say
3000 RPM) is generating 15Kw of electricity, and 60KW of heat!

I often need 15Kw electricity. I NEVER need 60KW of heat.


Andy