The concept of a perfect “green” house is 2.5–5 thousand square metres of energy-efficient housing on “passive” or secondary energy sources.
The Housing and Utilities Reform Assistance Fund and KORSA have been installing Russian heat pumps, adapted to national climatic conditions determined by ground heat transfer characteristics, in various regions of the country — Moscow Region, Kaluga, Kirov, Ryazan, Yaroslavl, and others — for more than 10 years.
The optimal solution was a house in Klin (Reshetnikovo village, Klin district, Moscow region), on the basis of which the concept of a model (reference) solution for an energy-efficient residential building was prepared.
The key parameter of the model house is its area. It is 2.5–5 thousand square meters of residential property, which is due to the need to reserve a certain amount of land for the location of the geothermal field of heat pumps. In terms of optimising heat loss, the Institute of Building Physics recommends that the house should be square at the base. The materials used for the building envelope and modern thermal insulation are also of great importance.
A fully energy-efficient house is a combination of solutions, including heat pumps, solar collectors and solar panels, depending on the region in which the property is located. Geothermal heat pumps also help to cool the rooms, which brings additional comfort and accelerates the payback period of the equipment.
With geothermal heat pumps, the room is cooled in passive mode, i.e. without switching on the heat pump, only by circulating coolant from the cold ground to ceiling or wall-mounted fancoils (internal fan coil units of the building air-conditioning system) installed in the building.
Tentative scheme of work with a geothermal circuit. Image: “50 Green Building Projects in the Moscow Region” survey
In the winter, the geothermal circuit provides heat for heating and hot water, while in the summer the presence of a ground soil mass cooled in winter makes it easy to remove excess heat from the building. This system is the most profitable, as the heat pump consumes no more than ¼ of the standard need of the building’s systems to compensate for heat loss. In cooling mode the heat pump is not switched on at all, only the circulating pump, which consumes almost no energy. This solution is much cheaper than traditional air conditioning both in terms of investment and running costs. For a house of 2,500 square metres, a heat pump with an output of about 140 kW is proposed. The best heating system for any type of energy supply is a floor heating system (essentially the same as a radiator, only spread out over the floor, giving a more even distribution of heat — such heating solutions have been made since ancient times, e.g. in China and Korea). The underfloor heating system also reduces the heating level of the heating medium, which creates additional savings in the energy supply.
Installing a heat pump of 140 kW for a house like this requires around 40 wells of 50 metres depth, which fully supply the heat pump with low-grade heat. The hot water supply is provided by a separate high-temperature heat pump, which immediately generates a temperature of 60 degrees (or 65) to meet the sanitary standards and regulations for tap water temperature.
The heat source is also a geothermal circuit. The characteristics of the geothermal heating and hot water circuit are determined by the frequency of use. The heating circuit is used seasonally — with a high load in the winter and rest in the summer (the earth is resting, there is a compensation of the heat taken away in winter from the bowels of the earth). The hot water supply is year-round. Therefore, the technological solutions for this circuit have been developed.
A geothermal heat pump, which provides hot water, uses a geothermal circuit as well as a drive-through cooler — an air heat exchanger — a dry cooler located under the roof of the building.
It draws heat from the apartment ventilation in the winter. Under sill dampers allow fresh air to enter the rooms. The dry cooler extracts heat from the ventilation of a 2,500 square metre building at a rate of around 10 kW per hour.
This heat (heat energy) is sent to the hot water system. In summer, the heat is extracted from the ambient air by the same dry cooler, at the same time recovering the temperature of the ground mass. The timing of the hot water draw-off is organised via storage buffers, with the equipment actively used at night at a special tariff. This storage system reduces the heat pump to its optimum capacity of approx. 50 kW. In summer, the heat pump output is increased to 100 kWh when using outside air and the ground as a source of low-grade heat.
Image: “50 Green Building Projects in the Moscow Region” survey
The entire heat pump system in the reference building consists of 4 pumps, operates under centralised control, automatically regulating the heating medium heating based on the ambient air temperature outside, i.e. weather-dependent. This system allows to carry out dispatching not only the results of work — on electricity consumption, on heat output, but also on the state of the equipment itself. In fact, diagnosis of each heat pump can be carried out online, including the possibility of remote adjustment and change of technical parameters. The operation of the entire heat pump complex is regulated by the automation, taking into account the uniform wear and tear of the equipment elements.
A set of such measures makes for a class A+ benchmark building.
The investment benefits are also taken into account when creating a green reference building. It is a long-term investment with an equipment life cycle commensurate with the life cycle of the building itself. The return on the technological equipment is about 7 years.
It consists of three parts. The first one is the heat pump, the second one is the geothermal heat pump and the third one is the heating substation. The geothermal circuit has a service life of over 50 years, the heat pump has a standard service life for such technologies and the heat pump operates for 30 years or more and at the end of this life the individual components — such as compressors — need to be replaced, although the cost of replacement is low compared with the total system. This replacement can easily be covered by accumulated funds for major renovation of the building itself.
Financial calculations show that with the average consumption of 1 GCal of heat from the heat pump costs about 1.18 thousand rubles, while the heat pump gives a cost reduction of almost 50%. Taking into account the improved building envelope, the total saving is 4 times compared to a standard building.
Residents of a house in Klin, where the above solutions have been implemented, are paying 80% less for heating and hot water compared to neighbouring houses (heated by a municipal boiler house). Mass implementation of such reference houses requires solving a number of problematic issues, including normative and technical issues.
The first is the lack of normative documentation for heat pumps (relevant building regulations (SB) are in development). The second issue is the installation of heat collection, i.e. drilling wells to install geothermal probes, which is not regulated in the subsoil use legislation.
The main issue is the interest of all parties involved in the investment, construction and operation of housing. Until this issue is resolved, the application of heat pumps depends only on the enthusiasm of individual innovators.
The key beneficiary in Reshetnikovo is the resident. At the same time the management companies are not interested at all in the application of these technologies and sometimes sabotage their work, not having their commercial interest. Therefore it is necessary to create conditions under which heat pumps will be really necessary in this particular case of application. Furthermore, in addition to the ecological effect they will also have a financial advantage for tenants, property management companies and investors.
Cover photo: fotoVoyager / iStock
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