An expansion of production of electricity from renewable energy sources is evident both internationally but also in Sweden. One renewable energy source that has great potential and access is solar energy, where solar panels is the prime and most used technique. The electrical system needs to be in a constant balance, this means that the production and consumption of electrical energy must constantly match each other. When solar panels get a bigger role in the world’s electricity production a need to store the overproduced electricity is born. A name for this type of storage is electrical energy storage (EES) and this can be the solution to achieve a flexible electrical system. There is a lot of different types of EES and it can be hard do decide its size. 

In this study calculation models were built to evaluate different EES for a building. On this building solar panels are planned and therefore a need of EES to increase the buildings self-sufficiency rate and self-consumption rate. The three different ESS that was studied was lithium ion battery, vanadium redox flow battery and hydrogen-based energy storage. Five different calculation models were built, one for the lithium ion battery, one for the vanadium redox battery and three different hydrogen-based energy storage were built all with their own set of conditions. The appropriate sizes of the five systems were calculated. For these systems the environmental impact, costs and payback time was also calculated.

Self-sufficiency rate and self-consumption rate is the highest for the two hydrogen-based energy storages 1 and 2. The self-sufficiency rate was 167% and the self-consumption rate was 100%. In these systems the total amount of solar produced electricity is used within the system.

All systems contribute to a decrease in operating costs if compared to the building without solar panels. The hydrogen-based system 1 answers for the largest decrease in operation costs, this system uses 456 kWh electricity per year compared to the system without solar panels who uses 11 600 kWh electricity per year. The shortest payback time for the EES systems answers to the vanadium redox flow battery at 29 years. The solar panels payback time is 25 years and their lifetime are five years longer at 30 years. This is a good sign for the development of the solar panels. If more money is given to the development of solar panels, they will most likely get more effective and more environmentally friendly.

The environmental impact results show that a system without solar panels has the lowest environmental impact at 11 070 kg carbon dioxide equivalents for at 30-year time span, if the impact of the Swedish electricity mix is considered. If the European electricity mix is considered the system with the solar panels has the lowest environmental impact and contributes to an emission reduction of -35 922 kg carbon dioxide equivalents over a 30-year time span.

The results make it hard to argument for the use of EES today. All studied ESS systems contributes to an increase of environmental impact and their payback time is longer than their lifetime which makes them a poor investment.