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Solar-Biomass Reversible energy system for covering a large share of energy needs in buildings

Periodic Reporting for period 2 - SolBio-Rev (Solar-Biomass Reversible energy system for covering a large share of energy needs in buildings)

Okres sprawozdawczy: 2020-11-01 do 2022-04-30

The SolBio-Rev project aims at the development of an innovative renewable energy system for the production of space heating, cooling, domestic hot water and electricity to meet all heating/cooling, and part of electricity demand of a building. The target is the development of a highly flexible configuration suitable for various buildings across EU, based exclusively on renewables.
The heart of the system is a novel reversible heat pump configuration coupled with multiple innovative renewable systems; adsorption chiller, evacuated tube solar thermal collectors equipped with thermoelectric generators (TEGs), a low-emissions biomass boiler with capability of high-temperature supply operating at combined heat and power (CHP) mode, and a smart control system.
The target of the SolBio-Rev is to reach high energy share in a variety of EU buildings. The overall aim is to test this new technology for one year and validate it in two existing, small-scale, pilot buildings to show its potential and define the necessary measures towards commercialisation.
The original key objectives of the project are listed below:
•Development of a cascade chiller with advanced heat exchangers to reach an electric Coefficient of Performance (COP) > 6 for space cooling production in south Europe
•Development of a reversible heat pump/ORC system using an environmentally-friendly refrigerant to reach a COP > 4.5-5 for solar-assisted operation and an ORC efficiency of up to 8%
•Development of an innovative evacuated tube solar thermal collector with TEGs to convert the otherwise wasted, lower-temperature heat into electricity
•Development of a biomass boiler for CHP operation with capability of high-temperature heat supply (up to 120 °C) and reduced air pollutants by over 20%
•Development of predictive and smart control
•Interaction with potential stakeholders for considering their needs during the design process and enhancing uptake across EU
•Realisation & testing of two SolBio-Rev prototype systems in small-scale pilot buildings at two diverse climatic zones (Greece, Germany)
•Validation of the SolBio-Rev concept based on the test results of the two pilots, for reaching an energy share of over 70%
•Definition of a technology roadmap, with suitable business models, aiming at commercialisation in 2025
Originally, the generic energy system was formed and adapted to different climatic zones. A preliminary feasibility analysis was conducted showing that a very high renewables share can be attained, reaching 80% for space heating, 70% for space cooling, 100% for DHW and 20-50% for electricity.
A small-scale reversible heat pump/ORC prototype has been developed using two scroll machines and the environmentally friendly refrigerant R1234ze(E). Simulations revealed that high performance is expected, reaching a net electric efficiency up to 5.90% in ORC mode. The system hosts multiple sensors and an automation system and is ready for testing under the different operating modes.
About the cascade chiller, experiments on the calcination of the sorbent material attained better adsorption and lower calcination temperatures. The sorption chiller has been built, while a custom-built heat pump was individually tested before being integrated with the sorption unit. Tests revealed that conventional heat pump operation can reach an EER up to 8 in temperatures similar to the ones of the sorption unit.
Regarding solar collectors, a separated design of collectors and TEGs was selected. Four heat conductivity pastes have been developed showing improved heat conductivity, while both commercial-based and printed TEG modules were tested. When passively cooled, the TEG prototype module attained specific power outputs up to 40 W/m2.
Referring to the biomass boiler, exhaust gas recirculation, air-staging and a new control strategy have been applied in a standard boiler. Testing has proven a significant reduction of CO and NOx emissions by over 50 and 25%, respectively, and an efficiency of up to 105%. Using an internal heat exchanger for CHP operation with the ORC, boiler efficiency exceeded 94%.
Concerning control, both a rule-based control strategy and a smart control have been developed using deep reinforcement learning to optimise the smart control for minimum operational costs. Control is being implemented in an automation server/DDC controller with control algorithms programmed based on the identified control point list.
Meanwhile, the pilot building to host the prototype system in Athens has been built while a containerized building in Nuremberg is being prepared.
A social survey with interviews and questionnaires on end-users and stakeholders of residential and office buildings across Europe has stressed the uptake potential. Environmental analysis with LCA has been launched focussing on manufacturing and end-of-life, while system integration in buildings is being examined.
Finally, dissemination and communication activities have been undertaken, with participation in various events promoting synergies with other projects and the production of the project logo, website, brochure, video and the participation in communication events.
Up to date, experimental results have been obtained for the adsorbent coating of the adsorption chiller, the heat pump to test the cascade chiller, the solar collectors with TEGs and the biomass boiler.
The optimisation of the adsorber design by UNIME, ITAE and FAHREN has revealed high performance and cost-benefit margin compared to state-of-the art zeolite adsorbers, thanks to the increased adsorbing capacity (~33%), and the reduction of the calcination temperature thus decreasing the manufacturing cost and time.
Regarding the reversible heat pump/ORC and the cascade chiller, experimental tests in an R1234ze(E) heat pump developed by DAIKIN and NTUA revealed that an electric EER up to 8 can be achieved in cascade chiller operation, while simulations resulted in COP values around 5, in solar-assisted heat pump operation.
About solar collectors and TEGs, AKOTEC produced heat conductivity pastes of increased thermal conductivity up to 47% against market products. However, the development stopped due to their limited service life. KIT has developed a novel fabrication process for high-efficient printable inorganic TEGs, with efficiencies matching their bulk counterparts, allowing also a scalable and cost-efficient production of TEGs.
Concerning the biomass boiler, ÖkoFEN and FAU have achieved through Exhaust Gas Recirculation, air-staging and advanced control, efficiency up to 105%, and a substantial reduction of CO (70%) and NOx (50%) and PM emissions. The addition of an internal heat exchanger for supply temperatures up to 110 °C for CHP operation, has reached boiler efficiency above 94%.
Regarding the whole SolBio-Rev system, preliminary simulations have envisaged high feasibility, reaching renewable energy shares up to 80% for heating, 70% for cooling and 100% for DHW. These results remain to be evaluated during the detailed simulations and tests performed in the two pilot buildings at NTUA and FAU. Testing will also demonstrate the key challenges of the systems integration, setting the ground for its further exploitation.
Finally, focus has been given on social aspects and dissemination to increase the social acceptance and awareness of the technology. Namely, higher income and aged 25-34 respondents were most likely to adopt SolBio-Rev’s core technologies.
SolBio-Rev Athens pilot building
Schematic representation of the SolBio-Rev concept