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Energy storage systems for family dwellings such as thermal and battery energy storage systems are of significant interest for several reasons, particularly in the context of increasing renewable energy adoption, ensuring grid resilience, and reducing environmental impact. This study examines the potential life cycle energy savings and environmental impacts related to the addition of the two energy storage technologies namely thermal such as a domestic hot water tank (DHW) and electrical which is a battery bank and attempts to evaluate the contribution of each component to the whole life cycle impacts. Moreover, the use of a second life electric vehicle Li-on NMC battery bank is examined as an optional replacement of a stationary battery bank LiFePO 4 . For a reference case is used a detached single-family house with a roof top photovoltaic system which has a compact exhaust air heat pump system to provide the hot water and space heating annual demand for the Swedish climate conditions. High resolution weather data and historic price data for the same year as well as stochastic occupancy profiles that include the domestic hot water load are used as boundary for a parametric simulation study for the system modelled in detail in TRNSYS 17. Main results show as far as the life cycle cost comparison that thermal storage has the least life-cycle cost among the three examined energy storage options. Examining the global warming potential of the first life of the electrical storage is found to be approximately more than 5 times the impact of the domestic hot water tank comparing the specific products from the two storage types.

Manufacturers' warranty specifications are commonly used as a reference for estimating the degradation of photovoltaic systems, which typically amounts to approximately 20% reduction in relative power after 25 years. Some premium manufacturers now provide warranties for up to 30 years, and efforts are underway to push for 50-year warranties. However, long-term degradation rate data are limited, especially given that over 85% of currently deployed modules have seen less than a decade of use. This issue is even more pronounced in Nordic European climates, where the PV market only started gaining traction in recent years. In this study, we evaluate the performance of a 3.2 kW PV system installed on a rooftop in Sweden in 1994. This system comprises 72 monocrystalline silicon PV modules, each with a capacity of 45 W, and has undergone multiple interventions over the years, including upgrades to power electronics and system configurations. In 2016 and 2024 the modules were tested, revealing a similar average degradation rate of 0.5%/year. Visual inspections were carried out, and apart from light yellowing, no other visible defects such as cracks in the solar cells, delamination, bubbles, hot spots, or rust in connection boxes were observed. © 2024 IEEE.

Operational control strategies for the heating system of a single-family house with exhaust air heat pump and photovoltaic system and “smart” utilization of energy storage have been developed and evaluated in a simulation study. The main aim and novelty of this study is to evaluate the impact on the benefit of these advanced control strategies in terms of performance (energy use and economic) for a wide range of boundary conditions (country/climate, occupancy and appliance loads). Short-term weather data and historic price data for the same year as well as stochastic occupancy profiles that include the domestic hot water load are used as boundary for a parametric simulation study for the system modeled in detail in TRNSYS 17. Results show that the control using a forecast of dynamic electricity price leads to greater final energy savings than those due to the control using thermal storage for excess PV production in all of the examined locations except Sweden. The impact on self-consumption using thermal storage of heat produced by the heat pump using excess PV production is found to decrease linearly with increasing household electricity for all locations. A reduction in final energy of up to 842 kWh year−1 can be achieved just by the use of these algorithms. The net energy cost for the end-user follows the same trend as for final energy and can result in cost savings up to 175 € year−1 in Germany and Spain due to the use of the advanced control.

Solar integrated building envelopes represent a significant energy harvesting potential in an era of decentralized building energy systems. This paper aims to simulate an energy system that consists of a transpired air solar collector component for a multifamily building cluster in Sweden. The energy system consists of an unglazed transpired solar collector in conjunction with air ventilation unit and exhaust air heat pump. The hot air from the solar collectors is used to increase the brine temperature at heat pump evaporator inlet to improve its coefficient of performance. The exhaust air heat pump is used to meet space heating and hot water demand for the buildings. The energy system is modelled using TRNSYS simulation program. The associated controls of the energy systems are optimized to increase the seasonal performance factor of the complete system, while maintaining the optimal performance of various subsystems. The quantification of the energetic benefits obtained from the proposed energy system is also presented using various key performance indicators. Furthermore, sensitivity analysis of different collector areas and operating variables such as airflow rate of the collector is conducted. The results show that the seasonal performance of the simulated energy system is 1.43 and the annual collector utilization factor is 0.18. Furthermore, the variation of the collector airflow rate has a positive impact on system performance, with an increase of 2 % in the annual heat pump coefficient of performance.

Renewable sources will play a key role in meeting the EU targets for 2030. The combined use of an aerothermal source through a heat pump and a solar source with a photovoltaic (PV) system is one feasible and promising technology for the heating and cooling of residential spaces. In this study, a detailed model of a single-family house with an air-source heat pump and a PV system is developed with the TRNSYS simulation software. Yearly simulations are run for two types of buildings and nine European climates, for both heating and cooling (where needed), in order to have an overview of the system behaviour, which is deeply influenced by the climate. The storage system (electrical and thermal) is also investigated, by means of multiple simulation scenarios, with and without the battery and with different water storage sizes. The numerical results provide an overview of the performance of the considered heating and cooling system, as well as the balance of the electrical energy exchange between the grid, the building, and the PV array.

Recently, decentralized household photovoltaic (PV) systems have become more affordable and there is a tendency to decrease subsidies for the PV excess electricity fed into the grid. Therefore, there is growing interest in methods to increase the self-consumption (SC), which is the part of the electricity produced by PV and directly consumed on buildings. It has been found that battery storage is an effective way to achieve this. When there is a heat pump system installed, thermal energy storage using the thermal mass of the building or hot water tanks, can also be used to increase the household self-sufficiency and minimize the final energy use. The main aim of this thesis is to develop operational control strategies for the heating system of a single-family house with an exhaust air heat pump, a photovoltaic system and energy storage. In order to accomplish this a detailed system model was developed in TRNSYS 17, which includes a six-zone building model and the heat pump control. Moreover, these control strategies include short-term weather and price forecast services.  Another objective is to evaluate the impact on the benefit of these control strategies in terms of energy use and economic performance for a wide range of boundary conditions (country/climate, electricity prices, occupancy and appliance loads).  Results show that the control using a forecast of dynamic electricity price in most locations leads to greater final energy savings than those due to the control using thermal storage for excess PV production. The exception is Sweden, where the result is the opposite. Moreover, the addition of battery storage leads to greater decreases in final energy than the use of the thermal storage (TH mode), which is limited to the thermal mass of the building and small hot water tank of the compact heat pump. As far as the impact of the advanced control (combined use of TH and PRICE) on cost savings is concerned, savings (up to 175 €) are possible in Spain and in Germany. The design of the TH and PRICE mode show low computational complexity that can be easily implemented in existing heat pump controllers. Additionally, the PRICE mode should have no capital and running cost for the end user while the TH mode might require an external electricity meter. Another yet implication with the TH mode is the need to activate the room thermostatic valve.

Operational control strategies for the heating system and “smart” utilization of energy storage were developed and analyzed in a simulation based case study of a single-family house with exhaust air heat pump and photovoltaic system. Rule based control algorithms that can easily be implemented into modern heat pump controllers were developed with the aim to minimize final energy and maximize self-consumption by the use of the thermal storage of the building, the hot water tank and electrical storage. Short-term weather and electricity price forecasts are used in some of the algorithms. Heat supply from an exhaust air heat pump is limited by the ventilation flow rate fixed by building codes, and compact systems employ an electric heater as backup for both space heating and hot water. This heater plays an important role in the energy balance of the system. A typical system designed for new detached houses in Sweden was chosen for the study. This system, together with an independent photovoltaic system, was used as a base case and all results are compared to those for this base case system. TRNSYS 17 was used to model the building and system as well as the control algorithms, and special care was taken to model the use of the backup electric heater as this impacts significantly on final energy use. Results show that the developed algorithms can reduce final energy by 5–31% and the annual net cost for the end user by 3–26%, with the larger values being for systems with a battery storage. Moreover, the annual use of the backup electric heater can be decreased by 13–30% using the carefully designed algorithms.

This study examines how the energy management optimization on household level affects the maximum power flow in a community of houses and the contribution to load smoothening in the community. A detailed model of a single-family house with exhaust air heat pump and photovoltaic system is used in combination with high-resolution weather, electricity use and hot water use data. All five houses in the community are identical but the occupancy of the residents and their use of electric appliances and hot water differ. Results show no reduction of the maximum power delivered to the grid if the houses are operated to optimize the individual self-consumption and self-sufficiency. The highest aggregated power from the grid for the whole community occurred when the heat pumps were controlled by the PV electricity production but without any battery storage. This case also resulted in least smoothing of the aggregated household loads in the community. The conclusion of the study is that energy optimization for individual households in a community do not have to result in a reduction of the aggregated load and power production.