Modeling of a hybrid heat supply system for typical rural houses

Abstract

Relevance: this article investigates the hybrid heating system (HHS) of a typical rural house, which consists of a combination of a traditional heating system with a boiler unit (BU), a hot water supply (HWS) with an electric water heater, and a system based on renewable energy sources (RES) such as a heat pump unit (HPU) and a solar collector (SC). In the proposed HHS, the main energy units based on RES are the vapor-compression heat pump unit (HPU) and the solar collector (SC). The main thermodynamic parameters of the HPU include heat output and the heating coefficient, while for the solar collector, the key indicators are heat output and collector efficiency. To determine these parameters for the object of study, an energy balance equation for the rural house with the HHS is proposed. Aim: is to model and study the hybrid heat supply system (HSS) of a typical rural house, which consists of a combination of a traditional heating system with a boiler unit (BU), hot water supply (HWS) with an electric water heater and a system based on renewable energy sources (HPU, SC). Methods: the work used methods of mathematical modeling, theoretical foundations of heat engineering, similarity theory, experimental study of heat exchange processes and generalization of experimental results. Results: the suggested mathematical model of the HHS for a typical rural house (1) allows for calculating the heat and electricity production and consumption, as well as the main thermodynamic characteristics for each hour of operation of the system’s key equipment. An analysis of the thermal balance of typical rural houses built in the Kashkadarya region revealed that for a typical rural house with a heating area of 144 m² and a heating volume of 432 m³, the average thermal load on the heating system is 13.8–14.0 kW, on the cooling system it is 10.1 kW, and on the hot water supply system it is 1.3 kW. The energy efficiency of using the HHS based on the HPU, according to our calculations, is 57–60%, meaning that the use of the HPU in heating systems for typical rural houses can reduce traditional fuel consumption by 1.57–1.60 times during the heating period. The use of the HPU in the heating period of a rural house with an area of 144 m² can save 1900 m³ of natural gas. With an average natural gas consumption in the heating period of 3300–4000 m³, the gas savings amount to 57–48%. The use of the SC results in savings of 33–27%, and the rational combination of “HPU + SC” provides savings of 75–90%.

English abstract from the paper. The authors’ abstract, reproduced under CC BY-NC-ND 4.0.

Keywords

• hybrid heat supply
• water-to-water heat pump
• rural house
• solar collector
• natural gas savings
• Kashkadarya

In plain English

The authors, of the Karshi Engineering-Economics Institute and the Belarusian National Technical University, model a hybrid heat supply system for a typical one-storey rural house in Kashkadarya region. It combines a boiler, an electric water heater for hot water, a vapour-compression heat pump and solar collectors, with a 5.0 kW photovoltaic array of 25 m² and the grid supplying electricity. An hourly energy balance links the heating and hot-water loads to the heat from each unit, using outdoor temperature and solar radiation for Karshi district over the heating season.

The house has a heated area of 144 m² and a volume of 432 m³, an outdoor design temperature of −13 °C and a heating load of 14.0 kW (97.2 W/m²); the hot-water load is 1.3 kW and the cooling load 10.1 kW. The heat pump chosen is a Mammoth J036WLE water-to-water unit with a heating output of 13–14 kW, an electricity use of 3.67 kW for heating and a coefficient of performance of 3.6–4.0; at 4.0 it gives 14.68 kW.

With a coefficient of performance of 4.0, compared with a boiler of 85% efficiency, the heat pump saves 0.74 kg of standard fuel an hour, or 2,344.2 kg of standard fuel (1,860–1,900 m³ of natural gas) over a 132-day heating season. Against a seasonal gas use of 3,300–4,000 m³ this is a saving of 57–48%; 28 m² of solar collectors save 33–27%, and the heat pump and collectors together 75–90%. The authors put the energy efficiency of the heat-pump-based system at 57–60%, cutting conventional fuel use 1.57–1.60 times. Bench tests of a small water-to-water heat pump in Karshi gave coefficients of performance of 2.1–3.5 with source water at 5–20 °C.

How to cite

G. N. Uzoqov, V. A. Sednin, B. M. Toshmamatov and B. I. Kamolov (2024). Modeling of a hybrid heat supply system for typical rural houses. Energiya va resurs tejash muammolari (Problems of Energy and Sources Saving), No. 4, 2024, pp. 132–140. https://doi.org/10.5281/zenodo.14580513