Solar Heat Pump Systems
Heat pump water heaters reduce energy consumption by up to 75% of a conventional electric water heater, hence reducing running costs and CO2 emissions. The advantage of a heat pump over other forms of solar water heating is the heat pump will continue to produce hot water at all times of the day at very low ambient temperatures.
The most efficient heat pump water heaters currently available will work down to minus 10 degrees Celsius, even without supplementary boosting. A heat pump water heater can cost a little more than a conventional water heater, however the running costs are in line with a solar water heater, depending on the contribution of the solar collectors to the total hot water demand.
The Compact Heat Pump Explained
A heat pump system is a form of solar water heating that does not rely on direct sunlight. Heat is extracted from the atmosphere using a refrigerant gas and compressor, commonly known as a heat pump.
The refrigerant liquid passes through a collector absorbing heat from the atmosphere and evaporating the refrigerant to a gas in the process. The heated refrigerant heated gas then moves along a coil wrapped around the storage where it condenses in to a liquid and heats the water in the storage tank.
The Compact solar unit is a hot water system that combines a heat pump with a Fin Coil evaporator thus creating a Solar Heat Pump Water Heater.
The system works on the principle of a refrigeration circuit, drawing heat out of one space and discharging it into another.
The Compact Solar Heat Pump consists basically of three major components. A compressor plus two heat exchangers (evaporator & condenser).
In operation, the evaporator absorbs whatever heat energy is available to it from the atmosphere (air) to vaporise the refrigerant. The vapour is then compressed raising its pressure and temperature.
This high temperature vapour is passed through special pipes permanently bonded around the outside of the water storage tank, forming the condenser. As the refrigerant vapour condenses back to its liquid form, it gives off its heat to the stored water.
As this happens, the condensed refrigerant liquid passes back to the evaporator panels through an expansion device (TX Valve), is vaporised, and the cycle is then repeated.
The refrigerant material (R134a) is unusual in that it has a very low boiling (or vaporising) point well below 0C at atmospheric pressure and a freezing point more than 100C below zero. It is liquid when cold but easily becomes a vapour when heated and vice versa.
The subject of hot and cold is really a question of relativity.
People think of hot and cold relative to themselves - their comfort levels.
As our normal body temperature is 36C an ambient temperature of +40C is called hot, while an ambient temperature of only +5C is said to be very cold. It is all relative.
In operation within the heat pump the refrigerant can be vaporising at a temperature of around minus 20C. An ambient temperature of +5C is HOT compared with such a low figure.
Thus a Compact Solar Heat Pump can operate in all seasons of the year, making hot water both day and night very efficiently.