| dc.description.abstract | One of the most efficient initiatives for reaching Norway's 2030 emission reduction targets is electrification. This electrification will increase the need for power transmission capacity, which in turn will require grid reinforcements in several areas. Grid reinforcements are time-consuming, costly, and often involve nature encroachments.
The electricity grid must have sufficient transmission capacity to cover peak power demand, even if the demand is significantly lower most of the time. The capacity demand in Norway has high seasonal variations, as space heating during winter makes up a large share of residential power consumption. This means that there is a lot of unused capacity in the summer.
The principle behind a seasonal thermal energy storage (STES) is to store surplus energy from the summer as thermal energy, and use it to meet thermal demand during winter. This thesis investigates how a community with a STES system can reduce the seasonal variation in its grid use, to see if STES systems can contribute to a more socioeconomically efficient development of the grid in the future.
This is investigated through a linear optimization model representing a community with 100 households, and by using the results from the optimization model as an aggregated load in a reference distribution grid. The community can invest in a STES and a photovoltaic (PV) system, and aim to minimize grid rent, electricity cost, and investment costs. The result is compared to two reference cases, one of which can only invest in PV, and uses panel ovens, while the other may also invest in individual heat pumps.
The model of the community with a STES showed a somewhat lower capacity demand and installed a larger PV system than the community with heat pumps. Even though the STES case installed more PV, the peak export of surplus power was lower, which indicates that having a STES system can make it easier to increase local energy production in a grid friendly manner. When the load profile of the three cases was added to the reference grid, the STES case increased the grid's peak load the least, even though the total yearly load was about the same as in the heat pump case. This means that the grid's transmission capacity was used more efficiently.
A 2030-scenario, with greater seasonal variations in electricity prices, and a separate export tariff was also implemented. In this scenario, the STES was used to cover more of the community's thermal demand, which decreased peak import and seasonal variations further. A larger share of the local energy production was also used locally, which lowers the risk of voltage violations elsewhere in the grid. The results indicate that STES can become a useful tool to enable more socioeconomically efficient grid development, especially in grids with limited transmission capacity. | |
