Hållbara uppvärmningsalternativ för hotellstugorna på Grinda : En kvantitativ studie gällande hållbara uppvärmningsalternativ på en skärgårdsö

Sammanfattning: Skärgårdsstiftelsen, which is responsible for several of the archipelago islands in Stockholm, has chosen to explore the possibilities for more sustainable heating systems in buildings on the islands in collaboration with KTH. A reduction of energy use and improving the efficiency of existing heating systems are included as part of the environmental work. This report studies the island of Grinda, which is located outside the area of Vaxholm in Stockholm. The study area consists of a guesthouse consisting of a restaurant as well as conference facilities and four neighboring cottages used for overnighting. The cottages now run solely on direct electricity, both for heating and hot water. The purpose of this report is to survey the current energy use of the four cottages with respect to the environmental effect and to propose alternative heating systems. In order to fulfill the goals and purpose, a literature study on energy use in general is conducted. Furthermore, models for water and energy use are developed. Based on their design, the new systems are limited to a heat pump solution with a ground or air source, a water heat pump, or a total solution with a pellet boiler which includes heating and hot water for both the guesthouse and cottages. The estimated cost for heating, hot water, and electricity for the cottages is 220 000 SEK. The required annual energy demand for heating and hot water is estimated at 151 000 kWh for the cottages. For the option of a ground source heat pump for heating and hot water in the cottages a power of 60 kW is required, meaning a payback period of 7.4 years. For an air-water heat pump solution, four separate pumps at 14 kW each are needed, which means a payback period of 7.0 years. The total solution with a pellet boiler is estimated to require two boilers at 80 kW each, and with the given input the payback period is 6.3 years. From an environmental standpoint, all three alternative heating options are more advantageous, according to this study. This is because electricity consumption can be more than halved with a heat pump; this applies to both ground source and air-water heat pumps. For the total solution with a pellet boiler more investigations should be done to obtain a proper environmental analysis. Important factors that should be investigated more thoroughly are the coefficient of performance for heat pumps, hot water use for the guests, and electricity prices.