Supply Temperature Stabilization of Decentralized Solar Thermal Collectors for Integration into District Heating System
ASHRAE Transactions. Vol.128, Part 1: 2022 ASHRAE Virtual Winter Conference 2022
Raimonds Bogdanovičs, Aleksandrs Zajacs

Energy-independent and self-sufficient buildings are a part of sustainable development. The share of houses with installed solar thermal collectors is growing. Collectors usually are used for hot tap water preparation but when there is no hot tap water consumption for a long time, the collector’s temperature increases that lead to collectors overheating, stagnation, and potential solar energy loss. Decentralized solar thermal collector connection to district heating system may solve stagnation problem, increase total solar energy fraction, and allow to remove the hot water storage tank from houses. In absence of local thermal energy consumption, energy can be feed into the grid and used by neighbors or accumulated in seasonal thermal energy storage. In such a way the household becomes a prosumer and can consume and produce thermal energy. The heat carrier must be injected into the district heating system with a defined temperature with a lack of temperature oscillations. The pressure in district heating may fluctuate, and solar radiation during summer cloudy days may vary pretty much, so it might be challenging to provide constant supply temperature from the solar collector system to the grid, which is confirmed by some existing solar thermal systems in the Central and Northern Europe. The solar thermal collector with return/supply connection to the district heating through a heat exchanger with a 3-way valve for temperature control was investigated. The study of supply temperature fluctuations and stabilization possibilities in northern climatic conditions was performed by an energy simulation software package and a test facility with flat plate and vacuum thermal collectors, that was placed on the university roof in Riga, Latvia. Here we report the experimentally discovered temperature fluctuation in different working regimes and different weather conditions, and the computer model validation results.

Control accuracy, Decentralized heat production, District heating, Prosumers, Solar thermal collectors

Bogdanovičs, R., Zajacs, A. Supply Temperature Stabilization of Decentralized Solar Thermal Collectors for Integration into District Heating System. ASHRAE Transactions, 2022, Vol. 128, No. 1, pp.453-461. ISSN 0001-2505.

Publication language
English (en)
The Scientific Library of the Riga Technical University.
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