power stations

[Willy Nilly]

At a guess, most of the energy that is put into a power station as fuel is lost to the atmosphere as heat through steam and exhaust, right?

So why not have smaller power stations nearer to where the power is needed and use the waste heat to heat building with? Wouldn't there be less transmission losses too?

There might be NIMBY problems, so just don't connect them to the grid.

[Simpo Two]

1) I doubt it; they are sure to have all sorts of energy-recovery devices.

2) A smaller power station will be less efficient

[anonymous-user]

http://www.worldcoal.org/coal-the-environment/coal...

give a lot of information on the subject of efficencies.

Eventually, however, cost is still king. There are loads of things that are technically possible from combined heat and power schemes to Carbon Capture etc, but as these all add cost to the final £/kWh they tend to be left out.......

[MartinQ]

I went to college in Widnes (leave it!) and the power station there was a CHP (combined heat and power) where the waste heat was piped to the local municipal buildings. You could tell where the pipes were routed because in the winter the snow and ice would melt above them.

[Engineer1]

There is an argument for CHP boilers in private houses and public buildings, but this is more of a green idea to improve a boilers efficiency.

[Nimby]

I remember seeing on TV a power station that has loads of tomato greenhouses on site. The waste heat is used to heat them. I don't know if the growing plants carbon-capture some of the CO2 from the furnaces - that would certainly accelerate growth as well as reducing emissions.

[Bobley]

Typical power stations achieve ~38-55% efficiency. Coal at the lower end, gas-fired combined cycle at the upper end.

Basic limitations come from thermodynamics. The steam in the turbines is expanded from ~180Bar/540°C (limited by the fatigue strength of the boiler heat exchangers) down to ~0.06Bar/38°C. 0.06Bar is a heck of a suck considering atmospheric pressure is 1.01Bar. When the wet steam leaves it must be condensed before being pumped back into the boiler and thats a massive amount of energy to loose.

The other heat loss is up the stack. You need a certain temperature to get the plume to rise. If you dont get enough heat then the you'll gas everyone around the power station!

Many contries have combined heat and power schemes and the power station is re configured to expand the steam to a more usable temperature (80-100°?) and this heat can be used in homes and offices. Here in blightly we missed the boat really but many large buildings (hospitals and large hotels for example) have mini-CHP systems. There are some new schemes starting on a larger scale....

http://www.chpa.co.uk/work-starts-on-coventry-dist...

[Sarkmeister]

CHP stations are fairly common in this country, and are usually linked up to heavy industry. The company I worked for had at least 7 or 8, each being around 30 or 40MW.

CHP linked to district heating systems is getting more popular, and is already very common in Sweden etc.

[phumy]

Bobley said:

Typical power stations achieve ~38-55% efficiency. Coal at the lower end, gas-fired combined cycle at the upper end.

Basic limitations come from thermodynamics. The steam in the turbines is expanded from ~180Bar/540°C (limited by the fatigue strength of the boiler heat exchangers) down to ~0.06Bar/38°C. 0.06Bar is a heck of a suck considering atmospheric pressure is 1.01Bar. When the wet steam leaves it must be condensed before being pumped back into the boiler and thats a massive amount of energy to loose.

The other heat loss is up the stack. You need a certain temperature to get the plume to rise. If you dont get enough heat then the you'll gas everyone around the power station!

Many contries have combined heat and power schemes and the power station is re configured to expand the steam to a more usable temperature (80-100°?) and this heat can be used in homes and offices. Here in blightly we missed the boat really but many large buildings (hospitals and large hotels for example) have mini-CHP systems. There are some new schemes starting on a larger scale....

http://www.chpa.co.uk/work-starts-on-coventry-dist...

Just to add a little to this post Combined Cycle Gas Turbine power plants are now reaching up to and over 60% efficency, especially the big new Siemens H style GTs and also Mitsubishi too. The reason for the heat going up the stack has nothing to do with heat having to rise to escape the power plant, the gases are driven out by huge fans, the heat is left in the gas on purpose due to the corrosive gases within the exhaust from the combustion furnace. The heat is kept in the gas to keep the gases in suspension as a gas and not allowed to drop to its "dew point" where the chemicals would "drop out" and be very corrosive to the near vicinity around the power plant.

[Timmy35]

The Nordics have some excellent pyrolysis waste to energy plants which operate at a local level. There's actually one on the Isle of Man. In terms of efficient overall it's excellent given the energy feedstock is waste that would otherwise be landfilled.

Small scale nuclear is also very viable and very safe now....think nuclear ships and subs.....power plants can actually be very small with modern technology, and using pebble bed reactors which are inherently safe.

Having said that given the fuss the enviro-mentalists are making over badgers and fracking at the moment the probability of us ever having efficient, safe small scale nuclear seems near zero.

[PlankWithANailIn]

Power stations are expensive, ugly and make politicians cough..thats why they site them in the places they don't go and where the land is cheep.

[ninja-lewis]

Nimby said:

I remember seeing on TV a power station that has loads of tomato greenhouses on site. The waste heat is used to heat them. I don't know if the growing plants carbon-capture some of the CO2 from the furnaces - that would certainly accelerate growth as well as reducing emissions.

British Sugar have a horticulture nursery next to their Wissington sugar factory. The excess steam from the factory is used to keep the greenhouses warm while the waste CO2 helps the photosynthesis process.

http://www.britishsugar.co.uk/tomatoes.aspx

The evocative footage of steam rising from Manhattan streets is down to condensation from the New York City steam system, which distributes steam from power plants around the city to buildings across Manhattan for the purpose of heating, cooling and powering them. Some businesses even use it for preparing food and cleaning.

http://en.wikipedia.org/wiki/New_York_City_steam_s...