What are water-to-water geothermal heat pumps, suitable in Romania

Heat pumps are efficient alternatives to central heating and air conditioning units.

In winter, these devices use electricity to transfer heat from a higher temperature space to a lower temperature space. In summer, the process is reversed. Because they transport heat rather than produce it, these systems consume less electricity.

For Romania’s climate, geothermal heat pumps are best suited. They take heat from the ground or water and transfer it to the house and are of two types: ground-to-water (heat exchange is with the ground) and water-to-water.

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Again, our country’s climate favors designs that harness water from the ground, i.e., water-to-water, so we’ll write more about them.

Water-to-water geothermal heat pumps, efficient but very expensive

Geothermal heat pumps are more expensive than air-to-water models (which do not require drilling), but have much lower operating costs because they exploit the relatively constant temperature of water deep in the ground. Energy costs for this technology are up to 60% lower than for air-water models, and the systems are more reliable.

For example, Daikin claims that its Altherma 3 GEO geothermal source pump model runs on 80% energy extracted from the ground and 20% electricity, with an A++ energy efficiency rating. With 1 kW of electricity, the heat pump is capable of delivering about 5 kW of heat. This model costs 43,000 lei (€8,700) for the 6 kW version.

For increased efficiency, pumps with inverter compressor technology should be chosen, which run non-stop at a variable output depending on the system’s need. On/0ff compressors are also available, with higher energy consumption.

Installing a heat pump is not possible in every household in Romania, as it depends on the size of the yard, the relief, whether there is water in the basement and what temperature it is.

Top water-to-water geothermal heat pumps can be connected to several heating systems: underfloor heating/cooling, radiators/heaters or fan coil units similar to air conditioners.

For running hot water in the bathroom and kitchen, these systems have a tank.

Drilling, a costly operation

Water-to-water geothermal heat pumps require vertical drilling to drive the pump deep into the ground.

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Vertical drilling can range from 40 to 200 feet. The more water that is drawn from the greater depth, the more efficient the pump will be. For example, a 180-metre vertical borehole provides access 365 days a year to geothermal water with temperatures of 17 to 20 degrees Celsius. At a depth of 40 metres, the water temperature in Romania is 11-12 degrees Celsius. We can see that after drilling a deep borehole, the heat pump does not have to heat the water very much in order to reach the temperature desired by the user.

When it comes to the price of drilling for heat pumps, it varies widely, depending on the hardness of the ground, the technology used (the work can be done with the customer’s electricity in the case of electrical systems) and the number of wells used.

In soil where probing is easy the cost can be 15 euro/metre, and in very difficult ones it can exceed 40 euro/metre. We thus see that a 40-metre borehole can cost between 600 and 1,600 euros, and a 180-metre borehole between 2,700 and 7,200 euros.

For a smaller house two wells are needed, one for water extraction and one for water discharge. Large houses or guesthouses require at least four wells.