Experimental Research of Control Algorithm for Solar Assisted Hybrid Water Heating System

摘要

District heating (DH) and domestic hot water (DHW) systems of Lithuanian cities and towns currently undergo process of renovation and alteration of the traditionally used fuels. First of all consumption of the expensive and dirty boilers' oil was reduced from 44.1% in 1998 up to 5.4% in 2009. Distribution of the fuels by type used in the Lithuanian DH systems in 2009 is shown in Fig. 1. Presently the main tasks of the Lithuanian heating economy renovation are implementation of the energy efficiency measures (first of all - relevant insulation of the heated buildings) and substitution of the expensive imported natural gas by the less polluting local renewable energy sources (RES). Share of renewable energy used for the DH and DHW production was progressively increasing during the last years step-by-step from 1.2% in 1997 up to 19.3% in 2009. According to the mentioned source of information, the main share of RES contribution to the heat energy production currently brings the wood fuel - 153450 toe or 90.15% of total RES fuels amount. Further development of CHP and DH systems in future years is also relied mostly on the wood and other types of biomass. We suggest taking into consideration other RES for including them into the space and DHW heating systems because of the following reasons: 1. Burning of wood and other types of biomass have some negative aspects (emissions of CO, NOx, VOCs, hard particles); 2. Utilisation of wood and wood residues from remote localities can be hard and expensive; 3. Some already existing heat energy technologies based on universally available solar irradiance can be used cost-effectively as independent heating systems or integrated into the hybrid heat energy installations; 4. Usage of wind energy for heating purposes can be also cost-effective in windy regions. Solar and wind energy technologies for generation of heat energy have a huge and untapped potential, which could be realised with benefit to environment and economy. Innovative heating systems exploiting wind and solar energy are considered in references [1-4]. In this paper results of solar assisted hybrid water heating system experimental research are presented.