May 21, 2019

Heat pumps

Greater benefit-Fewer pollutants

At a time when the search for alternative cooling-heating modes comes into the forefront, with the aim of reducing costs, heat pumps are presented as a fairly advantageous solution.

The large rise in the price of heating oil, coupled with the forthcoming adjustment to excise duty from next October and the overall economic situation, create the need to find solutions that reduce the cost of housing. This is because the sums of money we spend to cool or warm up our residence increase with geometric progress, greatly burdening the family budget. Heat pumps are presented as a quite interesting solution as we can reduce our costs by much. This is why, in most of the northern European countries, these systems are widely applied.

Thus, heat pumps can be used for cooling and space heating, presenting advantages such as lower operating costs than all known central heating systems. However, they have a higher purchase and installation cost compared to the existing technologies used. Finally, we should not forget that heat pumps have the smallest “energy footprint” in terms of environmental pollution and carbon dioxide (CO2), which depends on how electricity is produced.

What are Heat Pumps (GH)

Heat pumps are high efficiency heating and cooling appliances for domestic use and are used in other types of buildings. Their naming-categorization differs according to their mode of operation, taking into account two basic parameters.

The first parameter characterizes the medium used to extract heat from the environment (or is attributed in the summer to “cold”) and usually is the outside air. In larger installations, heat can be pumped either from the ground, which has a constant temperature of about 12 to 15 ° C, and the heat pump is characterized as a geothermal closed circuit of horizontal or vertical piping laying either from subsoil water (hot or cold ), of the sea or lake (the heat pump is an open circuit). In such cases, the heat transfer medium is water (with the addition of suitable antifreezes). The second parameter identifies the medium used to heat the building, and may be air (with or without a duct circuit), or water in underfloor heating circuits, fan coils, radiators, boilers,etc. As an example, split air conditioners are an air / air heat pump.

Typically, heat pumps consist of two parts connected to piping. The outside that draws heat from the environment and the indoor unit that delivers it.

In what follows, we analyze the operation of air-to-air heat pumps as they are more accessible to their installation, with the greatest appeal to the public.

 What is it and how it works with a heat pump system

An “air-to-air” heat pump, to which we refer, consists of the external and internal exchanger, the compressor and the relief valve. So, if someone wants to install such a system, they invite the company of their choice to do the appropriate study. During the study, the power and type of the system are selected to be efficient, and the respective siting of the individual parts is made. During the operation of the system, the compressor of the heat pump, operated by electric energy, compresses the gas refrigerant (the known freon), thus increasing its temperature and pressure. The heat of the refrigerant is delivered by means of a condenser either in the closed circuit of the heating water or in the indoor air of the building depending on the type of heat pump.

At the condenser outlet, the refrigerant has been liquefied. By using an expansion valve, the coolant is extinguished (its pressure is reduced sharply), resulting in cooling. By using a second heat exchanger, the coolant, through the exhaust, absorbs heat from the outside. The compressor then sucks the gas, refrigerant, thereby completing the refrigeration cycle. In the summer, this process is reversed by cooling the interior of the building and giving the heat to the environment.

  How much does a heat pump cost?

For a detached house of 150 sq.m. the air / water heat pump installation has an average installation cost of 7,000 to 12,000 euros. For the installation of the same water / water heat pump, the cost is from 8,000 to 15,000 euros, plus the cost of installing the geothermal heat exchanger, ie the pipeline network from which the heat of the soil will be pumped.

In this case, the efficiency of the heat pump is increased by at least one unit. The quality of the individual components, the accessories and the automation of the heat pump control, alter the price and operating costs. The market has a wide variety of heat pumps, given that they are manufactured by almost every well-known air-conditioning company.

Reduce costs by half

The issue of operating costs of the heat pump is up to date due to continued (upward) changes in oil and gas prices as well as the price of electricity (KWh). Accurate calculation of the operating costs of a typical air / water heat pump is difficult. Thus, at this year’s prices, if the average cost of electricity for a house is EUR 0.14 / KWh (due to a night and graduated charge scale) and the average efficiency of the heat pump is 3, then the cost of the energy produced heat pump heat pump is 0.14 / 3 = 0.046 euro / KWh. Accordingly, the cost of oil heating can be calculated as follows: The energy produced by combustion of one liter of oil in a typical boiler is about 10.8 KWh / lit and costs (average) 1 euro / liter. The cost of the boiler heating energy produced is 1 / 10.8 = 0.092 / KWh. If a house consumes about 2,000 liters of heating oil annually and pays around 2,000 euros / year, using a heat pump will pay 1,000 euros / year of electricity.

Based on the above, installing a heat pump in existing buildings is an economic and less technical matter that most homeowners will occupy in the near future. The optimal solution is a mixed system of heat generators, (existing boiler, heat pump and solar collectors) where, depending on the needs and external conditions, it will be chosen from a control automation, the optimum heat generation and storage unit.