Techno-economic optimization and analysis of a high latitude solar district heating system with seasonal storage, considering different community sizes

Abstract

A solar community meets a significant amount of its energy demand through solar energy. In a high latitude country like Finland, the seasonal mismatch of solar availability makes it very difficult to achieve high renewable energy fractions without seasonal storage. In this study, a solar community located in Finland was optimized with respect to energy demand and life cycle cost. To gain better understanding of both technical and economical scaling effects, the optimization was done separately for four cases with 50, 100, 200 and 500 buildings. The study was performed for Finnish conditions using dynamic TRNSYS simulations and optimized with a genetic algorithm, using the MOBO optimization tool. The modeled energy system had solar thermal collectors and solar electric panels for energy generation, two centralized short-term storage tanks and a seasonal borehole thermal energy storage system (BTES) for energy storage, and a ground source heat pump for additional heat generation. The larger communities provided noticeable cost-benefits when aiming for high performance. Larger seasonal storages allowed more direct utilization of seasonally stored heat, lowering the need for the heat pump and reducing electricity demand. Comparing the best and worst performing optimal energy system, annual demand for heating electricity was reduced by 80%. Renewable energy fractions close to 90% for heating were possible for all community sizes, but the large communities could obtain them with about 20% lower costs.

Cost-benefit analysis of district heating systems using heat from nuclear plants in seven European countries

“…Hirvonen et al [59] studied high latitude communities of different sizes from 50 to 500 buildings equipped with photovoltaic panels, SCs, a local DH network, a seasonal heat storage and a heat pump. High solar fractions (~90 %) were found to be possible for all community sizes, although large communities could achieve this with 20 % lower costs.…”

Towards the EU Emission Targets of 2050: Cost-Effective Emission Reduction in Finnish Detached Houses

“…Shifting the emission reduction burden away from individual building owners is another possibility. Seasonal thermal energy storage has shown significant potential in reducing emissions in Finnish communities of single-family houses when it is combined with solar thermal collectors [66] or distributed PV panels and centralized heat pumps [67]. The economics of solutions at different scales (individual house, district, country) need to be compared to find the best solutions.…”

Towards Optimal Sustainable Energy Systems in Nordic Municipalities

“…Comparing the simulated Balanced2020 scenarios with Demand2020 ( Figure 2), C tot (dr = 9%) increase between 2.2% and 12.9%, while CO 2 emissions are reduced to a minimum of 20. 6 Balanced2020 scenarios provide possible alternatives to achieve the near-zero balance condition as created by an EnergyPLAN user, without an indication whether the corresponding CO2 emission reductions are obtained with a minimum cost increase. On the contrary, the multi-objective optimization approach shall provide better knowledge of the alternatives that represent the optimal trade-offs between the two conflicting objectives of the MOOP.…”