Another element in installations that use solar energy by active systems is the heat pump. This device greatly increases the efficiency of active systems used for year-round heating. The heat pump replaces the heating devices, using conventional energy carriers. By her introduction, as an intermediate element of the system, more efficient work of the collector is possible (at a lower temperature of the working medium), as well as higher parameters of the refrigerant in the central heating installation. i c.w.u. There can be many solutions for a solar installation cooperating with a heat pump. Due to this, that the heat pump requires a heat source to operate (to the pump evaporator), these systems can be divided into such, where the heat pump gets its energy from the solar collector circuit (serial system), where it gets energy from another independent heat source: the ground, sewage, pond, wells, air (parallel system) and such, where there is a double heat source - direct and indirect.
Heat pumps have been known for a long time (in theory for over a hundred years), and after the energy crisis they were "rediscovered". These devices, depending on the type of energy supplied, can be broken down into:
1. Sprężarkowe pompy ciepła — gdzie energia mechaniczna lub elektryczna dostarczana jest do sprężarki (the most widely used).
2. Absorption heat pumps - where the heat is delivered to the cooker and evaporator. They use the properties of solutions consisting in increasing the boiling point of the solution in relation to the boiling point of the solvent. The following working media are used: woda — amoniak — czynnik roboczy — amoniak; water - lithium bromide - working medium - water; methanol - lithium bromide - working medium - methanol. Heating efficiency coefficient 1,2 — 1,8. Pumps of this type are less popular, although their advantage is quiet and trouble-free operation.
3. Termoelektryczne pompy ciepła — gdzie energię elektryczną dostarcza się do obwodu złożonego z dwóch półprzewodników, between the joints of which there is a temperature difference. One of the welds is below ambient temperature, the other above. The coefficient of heating efficiency is from 1,5 do 1,8. They can easily adjust the heating power, use them for heating and cooling, but their drawback is the high cost.
In the most widely used compressor heat pump, the principle of operation is this, that the working factor (e.g. mixtures of freons) it carries out a cycle called the Linde cycle, similar to the Carnot cycle backwards. The vapor leaving the evaporator is compressed to the required condensing pressure at the expense of the electrical energy discharged from outside N.
Steam in the condenser, walking through the liquid, gives off heat Q, then the liquid refrigerant leaving the condenser is expanded in the expansion valve and evaporates in the evaporator under reduced pressure and temperature. For this phase change, the required external heat Qo is extracted from various sources (water, grunt, household waste, air, etc.). The steam is compressed again in the compressor. The energy balance of the heat pump has the form
Q= Qo + N
The basic operational index of a heat pump is the coefficient of heating efficiency (efficiency of the heat transformation process) equal to the ratio of the thermal power q obtained to the delivered power.
The economic efficiency of using a heat pump depends on the level and temperature difference of the heat sources. In connection with, the most advantageous area of its application is low-temperature heating: air, planed ceiling and floor tiles. Currently produced heat pumps give 3- Up to 4 times more usable energy than they consume for the compressor's own drive. Compressor pumps are mechanically driven (engine) or electrically (electric engine). The upper temperature of the heated heating medium does not exceed 55 ° C.