In Almunge, east of Uppsala, there is a relative new health care center which has solar power installed on the roof. The solar cells annually produce approximately 62 000 kWh of electricity that are beneficial to store. Batteries can be used for short-term storage and to reduce peak power, but hydrogen storage can be used as long-term storage. Therefore, this study aims to evaluate if it is profitable to implement a hybrid energy storage compared to a single battery storage. The hybrid energy storage is a combination of a saltwater battery that reduces the peak power every month, and a hydrogen storage that functions as back-up power and long-term storage. This is compared to a single saltwater battery that is used to increase the self-sufficiency of the health care center. This is evaluated with respect to feasibility, profitability, sustainability and safety. In this study it turns out that it is not reasonable to install a hybrid energy storage using hydrogen both as back-up power and long-term storage, due to the risks. However, it could be feasible to install a hybrid energy storage where the hydrogens storage only act as back-up power. In the economic analysis, the lifecycle cost (LCC) and pay-back time were compared for five different energy storage solutions. The first solution is a hybrid energy storage, where the hydrogen storage act back-up power for three days, combined with a saltwater battery of 25 kWh to reduce peak power. The second solution is a hybrid energy storage, where the hydrogen storage act back-up power for seven days, combined with a saltwater battery of 25 kWh to reduce peak power. The third solution is a saltwater battery with a capacity of 60 kWh. The fourth solution is a saltwater battery with a capacity of 90 kWh. The fifth solution is a saltwater battery with a capacity of 120 kWh. It turns out that a saltwater battery of 60 kWh has the lowest LCC and shortest pay-back time that is shorter than its lifetime. Therefore, it is most profitable to install a saltwater battery of 60 kWh to increase the self-sufficiency of the health care center.

The increase of variable renewable source leads to an imbalance between the electricity supply and demand of the power grid, as the solar and wind energy production is weather dependent. By implementing battery energy storage system (BESS), the balance can be improved by storing energy when the supply is high and then use when the supply is low. The aim of this study is to investigate the profitability of implementing a BESS with a photovoltaic plant to the grid connected facility of Gävle Energi AB. This by mapping the potential revenues that can benefit both the property and power grid. The aim is also to investigate the cost saving of a BESS with an optimal control and then look at the sizing of the battery.   At the Swedish battery market there is two technologies, lithium ion and nickelmetal hybrid, both of which have different characteristics that affect its service life. The battery life is affected by its chemistry, state of charge, depth of discharge, charge rate, temperature, and operating conditions. One of the revenues with BESS are to take advantage of the price difference and charge the battery when the electricity price is low and discharge when it is high. The revenue is also to increase the self-use of solar power to the facility, peak shaving, and frequency control. You can also use the BESS as an emergency power due to its fast output power. The simulation was built in the program Excel containing eight different tasks, all with different battery sizes. Each task contained four control models; increase selfuse of solar power, peak shaving, frequency control and a combination of the three. This with input data from both 2018 and 2019.  The result showed that the best savings in all tasks occurred with the frequency control model or the combination model. The size of battery depends on the service life. The battery lift is hard to predict and thus also the choice of battery size. As the control model affects the battery life, the ideal battery life of 20 years can be difficult to achieve. Therefore, a BESS of 100 kWh may be recommended. Except as a property revenue, the BESS may reduce some percentage of marginal electricity and thus also the carbon dioxide emissions and may also support the power grid with frequency control.

A transition phase is taking place in Sweden, where the goal is to become a completely climate neutral country by 2045. The transport sector currently accounts for a third of fossil emissions in Sweden, while the transport sector also has the greatest potential to become fossil-free through, forexample, a comprehensive electrification. Bottlenecks in the grid is a challenge that Sweden faces where the existing ability to send powerthrough the country is already highly utilized. Battery storage can partly be the solution to this problem and also support the future needs that a further electrification of the transport sector may cause. Battery storage can, however, be both expensive and require a lot of space. To avoid this, the mobile battery storage that is available in electric cars can be used to convey power to the grid based on need. The technology that performs this bidirectional charging is called V2G (vehicle-to-grid) and has enormous theoretical potential. The number of electric cars in Sweden has increased by 82% duringthe year 2020, which provides good conditions for continuing to investigate the potential for V2G. Previous studies have shown challenges with the technology. The main issues pointed out have been profitability, winter conditions and battery wear, all of which are taken into account in this study. As in all of Sweden, Halmstad needs to plan for its electrification of the transport sector and load consequences on the grid. This study carries out a combined qualitative and quantitative case study that examines how a future electric car fleet can affect Halmstad's local grid. With data from HEM Nät from a winter week that will correspond to extreme conditions for the grid, a model has been developed in Excel to test different proposed scenarios. What is analyzed is how V2G can work in practice depending on where and when charging takes place, and whether power regulation can be profitable for both private individuals and network operator. Results show that some form of power regulation will be needed in the future to deal with the consequences of uncontrolled electric car charging with an ever-larger electric car fleet, and that V2G may be an option. Despite the winter climate and consideration for battery wear, a significant power peak reduction can be achieved if sufficient participation is attained and a good control strategy is found. Financial analysis shows a negative outcome for private individuals who use V2G. The utility services that is provided can on the other hand reduce costs for the network operator through load balancing incentives and reduced subscriptions to overlying networks. This in turn can enable an interest in network operators to introduce local incentives for private individuals' involvement.