Epsilon Archive for Student Projects

Abstract

The small-scale Mälsta farm near Knivsta is committed to sustainability, focusing on energy savings and self-sufficiency. The farm spans 4 hectares, including 3 hectares of arable and pasture land, supporting small-scale animal husbandry and household cultivation. Since 1994, energy efficiency measures such as solar and geothermal heating, solar panels, a water-jacketed wood stove, additional insulation, and LED lighting have reduced electricity consumption from 50,000 kWh to 12,500 kWh per year by 2022.
To further enhance self-sufficiency, Mälsta farm aims for 24-hour island operation, prioritized island operation for three weeks, and long-term total self-sufficiency in energy and sewage. Key strategies include expanding ground and roof-mounted monocrystalline solar panels and initially considering a vertical wind turbine. However, due to low wind speeds and high costs, wind turbines were deemed unfeasible. Instead, monocrystalline solar panels were prioritized. Despite their limited energy production period, they can provide a stable energy supply year-round when combined with storage solutions.
By collecting wind and solar data, simulations were performed to model energy production and compare it to the farm’s energy consumption. This analysis determined the optimal energy storage solution, which includes an 8000 kWh hydrogen system and a 30 kWh lithium-ion battery. The hydrogen system is intended for longterm energy storage from summer to winter, while the lithium-ion battery provides short-term storage for heating and lighting at night. Batteries are primarily used due to their higher efficiency, with hydrogen production occurring only when the batteries are fully charged.