On 18/06/2014 14:32, Johny B Good wrote:
Ok then, let me explain it this way:
A small home generator driven by an ICE is going to be chucking away
some 70 to 80 percent of the heat energy input from the fuel, in this
case Natural Gas. A gas central heating boiler is only going to
transfer circa 80% of the energy into the house, the rest going up the
flue.
If you size up the micro CHP plant to match the waste heat to the
original CH boiler, the generator output can be used to supplement the
grid supply, reducing the high wintertime demand.
At the very least, you'll be saving on electricity at an equivilent
cost of some 3 or 4 times the cost of the fuel's energy equivilent
with hardly any change to your consumption of gas.
In effect, instead of sending that 20% of waste heat up the flue,
you'll be sending the equivilent heat energy into the grid as high
value electrical energy.
I wouldn't get that excited.
It looks as though they are more efficient than conventional boilers -
but not by much. About 85% total, so 15% is going up the flue. It's
better, but not revolutionary.
What you do get is electricity generation inside that 85%, so it is a
good way to make power - but it isn't going to affect your gas bill. In
fact, if it's 6:1 heat
ower (which seems typical) you'll get slightly
less heat from your gas than a good conventional boiler!
Luckily most of the electricity will probably become heat too, so your
gas bill might dip slightly.
Andy (who has no mains gas)