To enable the transition to a fossil-free society and ongoing urbanization, where new establishments emerge in the heart of the society, the Swedish electricity system faces new challenges. Building a new powerline to meet the increased power demand is an expensive process, and in an existing grid, there isn’t always room to build new power lines. This leads to a capacity shortage at the local level, fundamentally due to the grid being undersized in areas where there are old power lines with lower rated current. To meet the increased power demand that electrification entails and simultaneously make capacity available for new establishments within the existing grid infrastructure, the potential of energy storage is being evaluated against the traditional solution of building new power lines.
The purpose of the present work was therefore to investigate whether energy storage can be a potential solution to make capacity available for future establishments in an area where there is a capacity shortage. The energy storage solutions were evaluated from an economic, environmental, and power quality perspective and compared to building a new power line. This was done from the perspective of a grid company, where neither the market of frequency stability nor the electricity price market were included in the analysis.
Based on the existing theory of energy storage, battery storage was chosen as the potential solution. To narrow the scope of the work, an area in Piteå Municipality was selected where a new establishment demands a power with drawal of 3 MW and is located midway between two existing grid lines. Using one year of operational data for the affected grid lines and calculations of their rated current, the performance of the battery storage was simulated, evaluating different battery sizes and energy contents (C-rate). Since the Electricity Act does not allow grid companies to own energy storage, the economic aspect was evaluated based on two different cases of battery rental. The goal is to maintain redundancy with the adjacent grid line with the additional power with drawal of 3 MW, to manage a potential outage without extensive consequences for subscribers.
The results of the calculations and simulations show that the current grid line can handle the extra 3 MW requested. However, the battery storage does not relieve the grid sufficiently to prevent exceedingthe maximum capacity of the grid during high loads while maintaining redundancy with the interconnected grid line. The battery storage needs to be larger than 3 MW to relieve the grid as required, which is not economically justifiable. Depending on the rental conditions of the battery storage and which revenues are considered, the profitability of battery storage varies, but with a battery size over 1 MW, regardless of rental conditions, it is not economically justifiable compared to a new power line, which has a significantly longer technical lifespan.
For battery storage to be useful in the grid and make capacity available, the grid must have spare capacity. The results also show that the relationship between the size of the establishment and the size ofthe battery storage is not one-to-one, instead, the energy content of the battery storage must be significantly larger to cut the power peaks. An energy content of two times the power, for example, 1 MW and2 MWh, is required for the battery to be advantageous and generate load savings on the grid. However, the battery storage can still relieve the grid to some extent by helping to distribute the current load more evenly, which means that the rated current, which is the limiting factor for short power line lengths, is not exceeded as early.
2024. , s. 37