Energy efficiency of a solar domestic hot water system

Abstract

Abstract. The solar domestic hot water (SDHW) system located on the campus of Bialystok University of Technology is the object of the research described in the current paper. The solar thermal system is composed of 35 flat plate collectors, 21 evacuated tube collectors and eight hot water tanks with the capacity of 1 m 3 of each. Solar facility is equipped with hardware for automatic data collection. Additionally, the weather station located on the roof of the building provides measurements of basic parameters of ambient air and solar radiation. The main objective of Regional Operational Program was the assessment of the effectiveness of this solar energy technology in the climatic conditions of the north-eastern Poland. Energy efficiency of SDHW system was defined in this research as the ratio between the useful heat energy supplied to the domestic hot water system and solar energy incident on the surface of solar panels. Heat loss from water storage tanks, and from the pipe network to the surrounding air, as well as the electrical energy consumed by the pumps have been included in the calculations. The paper presents the detailed results and conclusions obtained from this energy analysis.

A New Method to Determine the Annual Energy Output of Liquid-Based Solar Collectors

“…After determining the demand of domestic hot water EDHW and the solar fraction coefficient [8] and calculating the Esc value from Equation (1) or Equation 2, one can determine the required area of solar collectors : The procedure for estimating the required area or number of solar collectors based on the Esc value is described below.…”

“…Mostly designers assume an SCF value between 40% and 60%. This factor has lower values for tall buildings due to the small roof area in relation to the number of inhabitants [8]. In the case of a very good intensity of solar radiation, sometimes even 100% energy coverage for hot water by the solar collector system is analysed [14].…”

“…In addition, the data acquisition system reads the basic parameters of outdoor air and solar radiation every 5 s from a weather station which is located near the collectors. A detailed description of the project and the solar system implemented under this project are included in [7,8]. Figure 2 shows a simplified hydraulic diagram of the analysed water heating system supported by solar collectors.…”

A New Method to Determine the Annual Energy Output of Liquid-Based Solar Collectors

“…Figure 2 shows the distribution of in Poland using flat plate panels, and Figure 3 applies to evacuated tube collectors. Knowing the demand of domestic hot water QDHW, solar fraction SF coefficient [7], and calculating the value (Equation (1) or Equation (2)), one can determine the required area of solar collectors • m 2 .…”

“…The test object is located on the roof of the Hotel for Research Assistants on the campus of Bialystok University of Technology (Poland), and includes 21 evacuated tube collectors, 35 flat plate collectors with the total gross area of almost 150 m 2 , and eight tanks with a total capacity of 8 m 3 . Description of the research facility, and the project under which it was built, can be found in [6,7]. The EnergyPlus v. 8.3 software was used to carry out these simulations.…”