J. Eyem

Instchemas AB, Sweden,
iulius. evem@glocalnet. net.

Abstract

A heating system for family houses, consisting of directly connected solar heat collector (SHC) and heat pump was designed. The connection makes it possible to utilize both direct solar irradiation and heat contained in the moist air during periods without solar radiation. The designed system contains seasonal heat storage magazine consisting of the pit filled with a humid soil. The dense placement of the heat collector in the pit causes freezing of the water, which contributes to high content of usable energy, more than 40 kWh/m3 of the soil. The frozen soil is melted in the spring by means of warm brine from the SHC.

Keywords: solar heat collector, heat pump, latent heat, phase change material, heat storage magazine.

1.Introduction.

Solar radiation is the most abundant energy source on Earth. In spite of that, it is not used in large extent for covering useful energy demands of the human population. The diurnal and seasonal cycle of the solar radiation may be one of reasons, even though the wind energy, which is much less predictable and mainly much less dense energy source, is greatly subsidized in EU countries. While the energy density of the wind does not exceed 5-10 W/m2 and the accessibility generally does not come up to 30-35% of the annual time, the insolation can deliver more than 1 kW/m2 (heat) or ~50 W/m2 (electricity) with the accessibility in some areas more than 35% of the annual time.

The diurnal and at latitudes above 23° the seasonal variations of the insolation require storage of the solar energy in magazines with seasonal heat capacity.

There are principally two kinds of energy storage types: the chemical and the physical one. Quantitatively, some storage modes are suitable for large scale capacity storage, (GWh — TWh) some for the middle scale (1 — 1000 MWh) and others have just small scale capacity (less than 1 MWh).