• Energy Research

The transition to sustainable energy means much more than building more wind turbines and solar panels. An overhaul of the entire energy system is needed. The gap between supply and demand for sustainable energy is too large. In cities and industrial areas, where sustainable energy is most needed, there is a severe lack of space. And the deserts and oceans, where there is an abundance of sun and wind, are far away. This book shows how to solve these storage and transport problems in smart ways with hydrogen and electricity. In addition, we argue for a broader view of energy systems as part of an integrated, global system for supplying energy, materials, water and food. Let’s move ahead to green energy for all!

AbstractWe studied the possibility of converting waste toilet paper (WTP) into electricity. WTP is a waste stream with continuous availability and negative cost, but it is difficult to handle, as it contains fecal matter. The process we explored had two stages: WTP gasification followed by direct conversion into electricity in a high‐temperature solid‐oxide fuel cell (SOFC). The process was studied on a 10 ktpa scale by using real‐life parameter values obtained from industrial sources. We presented the basic system design, as well as its electricity yield and overall efficiency on the basis of detailed mass‐ and energy‐balance calculations. By explorative technoeconomic analysis and sensitivity analysis, we found an electric efficiency of 57 %, which is similar to that of a natural gas combined cycle plant. The levelized cost of electricity (LCOE) was 20.3 ¢ kWh−1, which is comparable at present to that of residential photovoltaic installations. The system's capital costs are relatively high, mainly as a result of SOFC investment costs, but we expect these costs to decrease as the market of cells develops. The operating costs are relatively low, partly thanks to the high thermodynamic efficiency (≈70 %). Currently, the fuel costs are negative (because we use waste as a raw material), yet this could change if the value of WTP would increase as a result of this process. Learning effects could make the system more competitive in the future with an LCOE of approximately 11 ¢ kWh−1.

This dataset is based on a full-scale research performed on two adjacent apartment buildings in Amsterdam. One roof has a bitumen surface with a solar PV system, the other is a blue-green capillary irrigated solar roof with grey (shower-) water suppletion, with a constructed wetroof for grey water purification. In the research, the solar output of both roofs was measured and compared, including temperature, irradiation and humidity measurements. The dataset covers 5 months, June to October 2022, and includes only day data (hours with solar irradiation).The dataset is being made public to act as supplementary data for publication(s) and the PhD thesis of Els van der Roest. Also, it might be used by other researchers.This dataset is a result of the TKI project Urban Photosynthesis and is co-financed with PPS fundingfrom the Topconsortia for Knowledge & Innovation (TKI’s) of the Ministry of Economic Affairs and Climate. Abstract of the paper:With an increasing demand for climate resiliency, water sensitivity, nature inclusiveness and energy efficiency in dense urban environments, the call for layered and multifunctional use of rooftops is rising. Vegetated roofs combined with Photo-Voltaic (PV) installations are an example of multifunctional and more effective use of available space, and well-irrigated systems could have an enhanced cooling effect. This research investigated a blue-green capillary irrigated solar roof with grey (shower-) water suppletion, with a constructed wetroof for grey water purification. Two full-scale commercial PV systems on twin rental apartment blocks in Amsterdam were analyzed, on a blue-green roof (BGR) versus a bitumen roof (BiR). The energy output, PV panel temperature, relative humidity and air temperature under the panels were monitored during 5 warmer months (June-October 2022). On average, a solar panel on the BGR is expected to produce 4.4% more energy than a solar panel on the BiR at similar irradiation. A clear difference in panel temperature on the roofs is only seen when the surface temperature of the roofs differs by at least 4.64°C. Otherwise, other factors such as wind or albedo have probably more influence on the PV panel temperature and thus on PV power output.

In the energy transition, multi-energy systems are crucial to reduce the temporal, spatial and functional mismatch between sustainable energy supply and demand. Technologies as power-to-heat (PtH) allow flexible and effective utilisation of available surplus green electricity when integrated with seasonal heat storage options. However, insights and methods for integration of PtH and seasonal heat storage in multi-energy systems are lacking. Therefore, in this study, we developed methods for improved integration and control of a high temperature aquifer thermal energy storage (HT-ATES) system within a decentralized multi-energy system. To this end, we expanded and integrated a multi-energy system model with a numerical hydro-thermal model to dynamically simulate the functioning of several HT-ATES system designs for a case study of a neighbourhood of 2000 houses. Results show that the integration of HT-ATES with PtH allows 100% provision of the yearly heat demand, with a maximum 25% smaller heat pump than without HT-ATES. Success of the system is partly caused by the developed mode of operation whereby the heat pump lowers the threshold temperature of the HT-ATES, as this increases HT-ATES performance and decreases the overall costs of heat production. Overall, this study shows that the integration of HT-ATES in a multi-energy system is suitable to match annual heat demand and supply, and to increase local sustainable energy use.

This dataset contains raw model results from 2 different scenario's as part of a publication on the the Power-to-H3 concept for system integration in a neigbhourhood energy- and water system. It is being made public to act as supplementary data for publication(s) and the PhD thesis of Els van der Roest. Also, it might be used by other researhers. The dataset was created during model runs in the period between January 2019 - April 2019. Abstract of the paper: 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.

This dataset contains raw model results from 3 different scenarios as part of a publicationon the utilisation of waste heat from a 2.5 MW electrolyser. It is being made public to act as supplementary data for publication(s) and the PhD thesis of Els van der Roest. Also, it might be used by other researchers.The dataset was created during model runs in the period between March 2022 - December 2022 as part of the H-Flex project.Abstract of the paper (published in The International Journal of Hydrogen Energy): Recovery of heat from electrolysers is potentially interesting to increase the total system efficiency, reduce CO2 emissions, and increase the economic feasibility of both hydrogen and heat production. This study examines different designs for the utilisation of (waste) heat from a 2.5 MWel polymer electrolyte membrane (PEM) electrolyser. Redundancy is important in the design, to ensure safe operation regardless of the heat demand of the heat consumer. We analysed cases with local heat consumption (with/without a heat pump) and coupling with a district heating network (DHN). Overall, 14-15% of the electricity input to the stack can be utilised by a heat consumer, increasing the total system efficiency to 90% (HHV) with CO2-savings of 0.08 (DHN)-0.28 (direct use) tonne CO2/MWhheat,used. We performed a first-order techno-economic analysis showing that the levelized costs of the electrolyser heat (8.4-36.9 €/MWh) fall within the range of other industrial heat sources and below lower-temperature heat sources.

This dataset contains raw model results ('SummaryFile_Raw.xlsx') from 10 different scenario's as part of a publication'Towards sustainable heat supply with decentralized mul-ti-energy systems by integration of subsurface seasonal heat storage' It is being made public to act as supplementary data for publication(s) and the PhD thesis of Els van der Roest. Also, it might be used by other researchers.Abstract of the paper:In the energy transition, multi-energy systems are crucial to reduce the temporal, spatial and functional mismatch between sustainable energy supply and demand. Technologies as power-to-heat (PtH) allow flexible and effective utilisation of available surplus green electricity when integrated with seasonal heat storage options. However, insights and methods for integration of PtH and seasonal heat storage in multi-energy systems are lacking. Therefore, in this study, we developed methods for improved integration and control of a high temperature aquifer thermal energy storage (HT-ATES) system within a decentralized multi-energy system. To this end, we expanded and integrated a multi-energy system model with a numerical hydro-thermal model to dynamically simulate the functioning of several HT-ATES system designs for a case study of a neighbourhood of 2000 houses. Results show that the integration of HT-ATES with PtH allows 100% provision of the yearly heat demand, with a maximum 25% smaller heat pump than without HT-ATES. Success of the system is partly caused by the developed mode of operation whereby the heat pump lowers the threshold temperature of the HT-ATES, as this increases HT-ATES performance and decreases the overall costs of heat production. Overall, this study shows that the integration of HT-ATES in a multi-energy system is suitable to match annual heat demand and supply, and to increase local sustainable energy use.

This dataset contains raw model results from 5 different scenario's as part of a publicationon the impact of system integration on system costs in a neigbhourhood energy- and water system. It is being made public to act as supplementary data for publication(s) and the PhD thesis of Els van der Roest. Also, it might be used by other researhers.The dataset was created during model runs in the period between July 2019 - April 2021.Abstract of the paper:The fossil-based energy system is in a transition towards a renewable energy system. One important aspect is the spatial and temporal mismatch between intermitted supply and continuous demand. To ensure a reliable and affordable energy system, we propose an integrated system approach, which requires the integration of electricity production, mobility, heating of buildings and water management with a major role for storage and conversion. The minimisation of energy transport in such an integrated system indicates the need for local optimisation. This study focuses on a comparison between different novel system designs for neighbourhood energy- and water systems with varying modes of system integration including all-electric, power-to-heat and power-to-hydrogen. A simulation model is developed to determine the energy and water balance and carry out economic analysis to calculate the system costs of various scenarios. We show that system costs are the lowest in a scenario that combines a hydrogen boiler and heat pumps for household heating, or a Power-to-X system that combines power-to-heat, seasonal heat storage and power-to-hydrogen (2,070 ���/household/year). Scenarios with electricity as the main energy carrier have higher retrofitting costs for buildings (insulation + heat pump) which leads to higher system cost (2,320-2,370 ���/household/year) than more integrated systems. We conclude that diversification in energy carriers can contribute to a smooth transition of existing residential areas.