Study On Economic Analysis Method Of A Heating System With A Water Pit For Solar Seasonal Thermal Energy Storage

A heating system with a water pit for solar seasonal thermal energy storage(HSWPTES)can store a lot of solar energy in the non-heating period and transfer it to the heating period,which is one of the important renewable energy technical routes for building clean heating.Good economic benefits are conducive to the popularization and application of the system.On the premise of meeting the heating demand,technical and economic analysis can provide guidance and support for reducing the heat price.This paper develops an economic mathematical model of dynamic thermal performance based on the dynamic simulation of the solar collector field heat gain and the temperature field of the water pit for solar seasonal thermal energy storage,in conjunction with the economic model of construction investment and financial analysis.It also realizes the dynamic thermal economics simulation of the whole system based on the TRNSYS simulation platform.The model enables dynamic analysis of the relationship between elements such as solar collector area,heat loss in a water pit for solar seasonal thermal energy storage,system control strategy,investment in major equipment,installation and commissioning costs,bank interest rates,return on investment,and system thermal performance and economy under different meteorological and solar resource conditions.This will make the calculation of system economy even more accurate and provide a reference for the optimal design of HSWPTES.(1)According to the work condition of the pilot project in Zhangjiakou City,Hebei province,the analysis point out that,When the internal rate of return is 8%,the heat price of a 100%heating system with a water pit for a solar seasonal thermal energy storage system is 0.513 CNY/kWh,which is 28.9%、27.9%lower than that of electric heating and natural gas heating.(2)The heat price under the variable flow constant temperature control strategy is 10.5%and 5.6%cheaper,respectively,than the heat price under the constant flow continuous control strategy and the temperature control strategy.Among the water pit for solar seasonal thermal energy storage(PTES)height to diameter ratio of 5:1,2:1,1:1,1:2 and 1:5,the heating price of the system is the lowest when the height to diameter ratio is 1:2,and the system economy is better.The heating price of the system decreases with the increase of sidewall inclination of the PTES,so when PTES in the system is cylindrical,the heat price is the lowest.The heat loss of PTES decreases with the increase of insulated floating cover thickness,but the cost of solar seasonal thermal energy storage increases PTES with the increase of insulated floating cover thickness Therefore,when the insulated floating cover thickness of the system is 0.4 m,the heat price is lower.(3)The solar energy resources are negatively correlated with system heat price,while soil conductive coefficient around the PTES is positively correlated with system heat price.The heat supply of the system increases with the increase of solar resources,so the heat price of the system increases with the increase of solar resources;The heat loss of PTES increases with the increase of soil conductive coefficient,and the heat supply of the system decreases with the increase of soil conductive coefficient,so the heat price of the system increases with the increase of soil conductive coefficient.(4)Through the static sensitivity analysis of the initial investment,loan ratio,loan interest rate,loan term,internal rate of return,project calculation period and operating cost of the system.It can be known that the value-added tax rate in the economic analysis model is most sensitive to the influence of heat price,while the operation and maintenance ratio is less sensitive to the influence of heat price.