Optimization and techno-economic analysis of combined gas-fired boiler and solar heating system for capacity-increase cities

With the worldwide rapidly increasing urbanization, the demand for heating increases too. To meet the substantially higher heating-demand, traditionally, the number of gas-fired boilers is simply increased. Unfortunately, this also causes severe air pollution. A viable alternative is solar heating systems that could be added to the existing gas-fired boilers system. This study investigates a heating system, which combines solar heating and existing gas-fired boiler heating into one system. The optimal individual capacity of the system is determined and the operation characteristics, energy saving, and economics are analyzed. The results showed that the combined heating system has a clear advantage with respect to both energy saving and economics over the traditional solution (gas-fired boiler-capacity expansion). For an increase rate of 20% for the heating areas, for example, the average energy-saving rate is as high as 69%. With increasing capacity, the difference per unit heating-area cost between the two systems increases. This means that the combined heating system is even more beneficial when the capacity increase is high. This study shows a new way to meet increased heating demand effectively, which is especially useful for cities that require a significantly-increased heating capacity.