You need to have all your heating satisfied by the E7 schedule, else its more expensive. Everyone knows its half price at night, but not everyone knows the daytime tariff on E7 is higher, and the saving thusly goodly shrunk. Its easy to end up paying more on E7.
NT
Airton model AS-12HR53 - bought at Brico Depot in France. They have a conveniently placed store at Calais tel. 00 333 21 17 07 23
Russell.
Where I live the climate is very dry so this is less of a problem.
Now, what area of solar plate will I need to gain 3900 W? Can I get one that works at night when it is coldest outside? Can I install it for 260 Euro?
Russell.
Unfortunately gas is not an option here. Note also that the cost of gas is rising with the cost of oil and North Sea reserves are low.
Russell
iirc, there is some scheme in the UK whereby you can claim some/all of the VAT back if you install a reversible aircon unit.
sponix
I always thought that was the case, but when a mate looked into it with his supplier (I forget which) he found that the day time rate was actually exactly the same as the suppliers normal tarrif. The sting was that the E7 tarrif had a higher standing charge.
What do you think most of the power stations run on then? ;-)
A 24 hour base load /will/ work out slightly cheaper on economy 7. Some regions (did) charge no extra for daytime units. East midlands was one. Whether that still applies is another matter.
VAT *is* 5% on domestic /reversable/ aircon.
What source of heat? At startup the air temp in and out is the same so there is no heat differential or 'source of heat' unless you put something hot in the fridge.
if the OP's kit produces more heat than the energy input then it should be a matter of simple engineering to make the apparatus power itself and produce heat with no energy input at all - explain!
cheers
Jacob
PS and there are laws of thermodynamics - have they been changed recently?
Heat pumps do not generate heat; they move heat from one location to another. Heat is moved from the outside air, water or the ground into buildings for heating and DHW. On average heat pumps consume one third of the electricity of electric resistance heaters. Sounds good so far.
Heat is found in what most people would regard as cool or cold points. Even on a very cold day there is heat energy in the outside air. The temperature of air would need to be absolute zero, -273C, for no heat energy to be available. On a freezing -1C day, the air temperature is -272C above absolute zero. 20C is 293C degrees above absolute zero. So, a heat pump only has to raise heat a relatively small amount; the refrigeration cycle does this.
A heat pump is a large refrigerator compressor. The compressor raises the pressure of the refrigeration gas and subsequently the gas temperature. Heat energy is concentrated by the compressor. The absorber has a similar function to an icebox in a fridge, absorbing heat, being either an outside air-to-air radiator, a buried pipe in the ground or a water-to-water heat exchanger in a stream or pond. The emitter, performs a similar function to the warm pipes at the back of a fridge, is the hot water storage vessel, heat distribution pipework or ductwork heater battery inside a house.
Heat pumps may incorporate reversible compressors to provide cooling , typically incorporated within a forced air ventilation system. Generally in temperate climate UK, heat pumps are only capable of providing comfort cooling rather than full cooling, as heating is the prime function. Cooling is unnecessary in the UK if proper insulation, ventilation and shading is fitted. In other countries heat pumps may provide full cooling.
The cooling aspect of heat pumps offends environmentalists, who frown on summer cooling using fossil fuel as the root power source. Although a heat pump can theoretically recover maybe 7 kilowatts from every kilowatt used, the overall efficiency from power station to recovered heat is around 30%.
Gas is about 1/4 to 1/3 cheaper than electricity per kW to buy. Heat pumps on average are 1/3 cheaper to run than electric resistance heaters, bringing them "near" to the running cost of gas. Electricity from power station to point of burn is about 30% efficient, because of latentent heat and line losses. So, may as well burn natural gas at point of use, which is about
86% efficient using the 100% scale. Gas overall is cleaner, cheaper to install and run. 95% of all Heat pumps in the UK are in commercial installations. They are not actively encouraged by governments as they use dirty electricity.
Solar panel cost only the running of small pump. You can store the heat in a thermal store and use low temp UFH to use during the night or cloudy days.
Does this mean 30% as against 700%, i.e. still a gain but small?
Gas fridges are not uncommon - why can't gas be used directly in heat pumps?
What about my point that apparatus with net power gain could power itself and produce heat with no energy input at all?
cheers
Jacob
The generation process converts high grade heat into electrical energy. The maximum efficiency from thermodynamics is:
eff = (T2 - T1) / T1 where T is in Kelvin, ie 273 + deg C
Typically T2 is very high and T1 is hopefully closer to room temperature to get a high efficiency. Usually there are significant losses such that overall generating efficiency rarely gets above 40% and is more typically
30%.When it comes to heat pumps the equation is the other way round where you're now creating low grade heat.
eff = T1 / (T2 - T1)
Typically ( T2 - T1 ) is a few 10's of degrees in 300 or so in theory the efficiency should be 1000% or 10 times the energy input. In practice losses make this nearer the 300% as quoted here.
Ammonia absorption fridges are something else and very complicated. Have a look at:
I'm not convinced about the low temperature performance. I doubt it would work with an outside temperature less than 10 deg C. Anything lower and ice will form very quickly reducing the heat exchangers efficiency. How quickly do you think ice will fill the gaps between the fins?
They are slow to operate and recover.
A Perpetual Motion Machine. No one has managed that yet.
A heat pump can output more energy than what it takes to operate (in fact it only moves heat). But the problem is changing the heat it outputs (energy) back to a form of energy that can turn the heat pump. The energy state change from heat to electricity saps up any surplus energy. You have the notion of a heat operated heat pump. The output of the heat pumps is not hot enough to drive an absorption refrigeration system.
A machine that outputs more than what it takes to run, is referred to over-unity. A heat pump is not over-unity as it "moves" heat.
If I have a 100 litre cylinder full of 80C water and another cylinder cold, I could run a small cheap pump to move the hot water from one cylinder to the other. That is a quite a bit of heat energy that the pump has moved for little energy input to run the pump. The heat moved in reality is not the pump output, although it appears that way.
I guess it varies then, when I was on E7 it was more money in day time, we changed to flat rate and saved money.
Last time I looked at leccy prices there was a wide variety in different regions.
NT
They are ideal candidates for cars as they can use waste heat from the engine rather than consume power from the crank as the current a/c systems do. The problem was that they are slow to respond so were never taken up. If the car is baking hot inside and you want the inside cool ASAP an electric compressor can do that. An absorption a/c will take a long time, so not that practical for cars. But, PV cells integrated on the roof of a car can keep the absorption a/c system ticking over and a slow moving fan running to keep the interior cool while parked. When the engine starts up, a heat accumulator (as on the US Toyota Prius) storing high grade heat, can give the a/c system a boost until the waste heat from the motor kicks in. All now feasible with few moving parts.
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Wirh air sourced heat pumps, heat is extracted from the outside air. Most domestic air sourced heat pumps in the UK have a maximum output of around
5kW (17,000 BTU/h). The problem with air source is that outside air temperatures may fluctuate widely affecting heat pump performance.Air-source heat pumps work very well down to around 7C, below, efficiency depends on the heat loss of the building being heated. If a building is well insulated with a low heat loss, an air-source heat pump can efficiently heat a house with an outside temperature down to -4C, or lower. A poorly insulated house will require a supplemental heat source to assist at an outside temperature around freezing.
Air sourced heat pumps operate at temperatures colder than 7C degrees for much of the winter. When the temperature is -7C degrees and below, efficiencies drop off sharply, with a COP 3 rated heat pump being closer to COP 2 or COP 1 than COP 3. When outside temperatures fall below 5C the heat pump may require periodic defrosting. The heat pump extracts heat from the house to heat the outdoor coils lowing efficiency further.
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