Although it seems contradictory, can be generated cold from heat. This fact is very attractive, since it is in summer when greater demand of cold has and greater availability of thermal solar energy appears.

It is possible to cool a house with the same radiating ground installation whereupon it is warmed up in winter. In order to heat it is made pass water hot and to cool cold water. But nevertheless, in summer it is necessary to dehumidificate the atmosphere. For it they will have to install dehumidificators Fan-Coils.

The absorption machine

The absorption machine was invented in 1859 and the operation system is very similar to the one of a refrigerator or pump of heat. Basically the mechanical compressor by a thermal system of evaporation and absorption is replaced, being equal the circuit of the coolant.

Connecting a refrigerator by absorption to a thermal solar installation it would be obtained, in addition to hot water and heating in winter, hot water and refrigeration in summer. But this option presents/displays some disadvantages.

The absorption technology allows to take advantage of the heat a fluid to 70 - 95 ºC to generate cold, presenting/displaying a coefficient of efficiency COP very strongly related to the temperature. The COP oscillates between 0.7 is 1.4 according to the temperature of the hot fluid is in limits inferior or superior.

The solar receivers, when depending on the sun, cannot guarantee a constant provision of hot water to the wished temperature. In order to guarantee necessary the refrigerating power of a house, he will have to sobredetermine the proportions the absorption equipment and to settle a boiler of support to warm up the hot fluid when he does not arrive at the wished temperature.

The solar collectors of vacuum tubes are most appropriate to obtain an optimal temperature for the operation of the installation, but much more expensive that the flat receivers.

The cost of an absorption machine already is elevated of in case. To this it will have to add to it him the one of the installation and its components, as well as the one of the fuel consumption of the support heater.

In addition, the installation needs a cooling tower, a conflicting element at the present time to be bed of culture of legionela and that needs constant maintenance and a special location.

All this causes that the use of this system is not the best form to cool using renewable energies, being little economic, with a high initial investment, and having the necessity of constant maintenance.

The alternative

The equipment of conditioned air or conventional heat pump obtains better coefficient of efficiency COP, around 3.5 4.5, with which the power saving is much greater.

In addition, the cost of investment and maintenance are lower, and its extended technology more in the market.

For its operation they consume electrical energy that can take place of clean and gratuitous form with photovoltaic solar paddles. These adapt very well since in summer, when there is more necessity to cool, they can generate more amount of energy because there are more hours of sun.

The cost of a photovoltaic installation, in addition, is subsidized by the state and can be connected to the installation to network to sell the generated electricity and to obtain to benefits, amortizing before the investment.

Using the same power plant, the sun, this system obtains better yield with one more a simpler installation, with no need of maintenance and a much smaller initial investment.

If it is desired to cool in summer and calefactar in winter, is very advisable to install a heat pump with radiating ground and dehumidificators. The system allows to use solar thermal collectors for heating and photovoltaic panels for the electrical consumption.
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