Influence of technical failures on the performance of an optimized community-size solar heating system in Nordic conditions

Abstract

There is a substantial need to accelerate the advancement and implementation of clean energy technologies in order to solve the challenges of the energy crisis and climate change. Solar heating technology is a feasible solution among clean energy technologies. In real conditions such complex systems often suffer from different kinds of technical failures and deviations reducing the system performance. This paper focuses on the challenges of a solar district heating system at high latitudes, proposes an optimized solution and investigates the influence of possible failures in planning, implementation and operation phase. The configuration proposed is a heat pump connected between two tanks, using solar-charged borehole storage to directly charge the lower temperature tank. Dynamic simulations were performed and a multi-objective optimization was carried out. The impact of the considered system solutions on the renewable energy fraction, purchased electricity and investment cost as a function of demand, solar thermal and photovoltaic areas, tanks and borehole volumes have been evaluated. The influence of 10 different technical failures was investigated. The study showed that in the optimized system, the most serious faults were i) de-stratification of the storage tanks (23-35% increase in annual purchased electricity) ii) on-off instead of variable speed control of the solar circulation pump (1-22% increase) and iii) reduction in heat pump performance (7-21%). These numbers of course depend on the initial assumptions, but still they show the magnitude of performance reduction some failures can achieve. Therefore, these parameters need to be considered during the implementation of such a system.

Challenges Associated With The Construction And Operation Of Seasonal Storage For A Small Solar District Heating System: A Multi-Objective Optimization Approach

“…Nevertheless, under realistic operation setup, the monitoring data indicated that a solar fraction between 21% and 33% is attainable [8]. Higher solar fraction value has never been obtained as a result of many problems such as higher heating demand in comparison to expectation, increased thermal losses in the seasonal storage, and reduced heat exchanger and solar collector efficiencies [7]. Similar problem has been detected in other SDHS installed in Rockstock and Neckarsulm [9].…”

“…Unsurprisingly, performance has not been at par given that the theoretical models used in pre-studies discuss performance under ideal conditions. Many operational challenges have to do with the wrong application of various technologies [7].…”

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

“…Regardless, simulated studies are sure to be overly optimistic as real systems always suffer from unexpected problems, such as component failures, less than ideal efficiencies, uncontrolled ground water flows and different than expected environmental conditions. Such technical problems and non-ideal behaviour have been studied in (Rehman et al, 2018). (Nussbicker et al, 2004;Schmidt and Mangold, 2006 with the Finnish case in this study.…”

Towards positive energy communities at high latitudes

“…Moreover, various combinations of storages, renewable energy generation and electric vehicles are compared, both technically and economically for cold conditions. The renewable district heating system, seasonal storages and buildings have been simulated and optimized in earlier studies [48,49]. In the current paper the focus is on the optimized integration of the renewable electrical generation system, electrical storages, grid connection and electric vehicles in the community and the comparison between various combinations (technically and economically).…”

“…The research aim and objective of this paper is to facilitate and propose the rollout of the community-scale renewable electricity systems in Finland and also to widen the optimization study made in the previous work [48,49], where community-scale renewable district heating system is only studied. The electrical, heating systems and buildings in the community are integrated, optimized and studied together in the present paper.…”