In the transition from fossil to renewable energy, the energy system should become clean, while remaining reliable and affordable. Because of the intermittent nature of both renewable energy production and energy demand, an integrated system approach is required that includes energy conversion and storage. We propose a concept for a neighbourhood where locally produced renewable energy is partly converted and stored in the form of heat and hydrogen, accompanied by rainwater collection, storage, purification and use (Power-to-H3). A model is developed to create an energy balance and perform a techno-economic analysis, including an analysis of the avoided costs within the concept. The results show that a solar park of 8.7 MWp combined with rainwater collection and solar panels on roofs, can supply 900 houses over the year with heat (20 TJ) via an underground heat storage system as well as with almost half of their water demand (36,000 m³) and 540 hydrogen electric vehicles can be supplied with hydrogen (90 tonnes). The production costs for both hydrogen (8.7 €/kg) and heat (26 €/GJ) are below the current end user selling price in the Netherlands (10 €/kg and 34 €/GJ), making the system affordable. When taking avoided costs into account, the prices could decrease with 20–26%, while at the same time avoiding 3600 tonnes of CO₂ a year. These results make clear that it is possible to provide a neighbourhood with all these different utilities, completely based on solar power and rainwater in a reliable, affordable and clean way.

The application of sulfate reducing bacteria (SRB) to treat municipal wastewater is seldom considered. For instance, due to low sludge yield it can reduce the amount of excess sludge produced significantly. Several studies, mainly at laboratory-scale, revealed that SRB can proliferate in artificial wastewater systems at temperatures of 20°C and lower. So far, the application of SRB in a domestic wastewater treatment plant has been limited. Therefore, this study evaluates the proliferation of SRB at pilot-scale in a moderate climate. This study revealed that SRB were present and active in the pilot fed with domestic wastewater at 13°C, and outcompete methanogens. Stable, smooth and well-settled granule formation occurred, which is beneficial for full-scale application. In the Netherlands the sulfate concentration is usually low (,500 mg/L), therefore the application of SRB seems challenging as sulfate is limiting. Additional measurements indicated the presence of other sulfur sources, therefore higher sulfur levels were available, which makes it possible to remove more than 75% of the chemical oxygen demand (excluding sulfide) based on SRB activity. The beneficial application of SRB to domestic wastewater treatment might therefore be valid for more locations than initially expected.