Net zero energy buildings (NZEB) and nearly zero energy buildings (nZEB) are a major subject of study in Finland and abroad. Such buildings are assumed to be both consuming minimal amounts of energy, as well as generating on-site energy through renewable energy technologies. Solar energy is often considered due to its easy installation on the roofs of houses. However, solar energy is intermittent and often the generation does not match with demand. Using biomass for small-scale generation of combined heat and power (CHP) is another option. With CHP, the output can be controlled, but heat and electricity are rarely needed in the exact ratio that they are generated. Often small-scale energy generation systems are less efficient and more expensive than larger systems. Individual buildings are also limited in how much they can adjust loads to match generation. Community energy systems allow the use of local energy, while benefiting from a more balanced load profile, lower investment costs and efficiency improvements. This thesis shows that roof-top solar electricity systems in Finland require financial support to be economical. However, thermal storage and demand response can be used to significantly alter the economics. While large solar energy systems are much cheaper by unit price, the energy matching problem is made worse by overcapacity and prevents individual buildings from completely benefiting from the economies of scale. Community-scale solar energy systems were found to be economical even without support payments. In case of controllable CHP, joint controls of equipment were found to be extremely important to gain the benefits of shared energy. Community-scale allowed the use of seasonal thermal storage, which is a key technology for achieving a high degree of utilization of solar energy in Finland. Instead of zero energy buildings, we should shift to developing zero energy communities, which can benefit from the best features of both distributed and centralized energy systems.
|Translated title of the contribution||Kohti nollaenergiayhteisöjä: Paikallisen ja uusiutuvan energian hyödyntämisen tehostaminen rakennuksissa käyttäen jaettua energian tuotantoa ja varastointia|
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- zero energy communities
- renewable energy matching
- seasonal thermal energy storage
- multi-objective optimization