| 1. |
- Schweiger, Gerald, et al.
(författare)
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The potential of power-to-heat in Swedish district heating systems
- 2017
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 137, s. 661-669
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Tidskriftsartikel (refereegranskat)abstract
- The main challenge for future electricity systems is to match the available electricity from variable renewable resources with the electricity demand in place, time and quantity. One option for increasing electricity system flexibility is to integrate the electricity system with the district heating systems via the use of power-to-heat technologies such as electric boilers. The overarching objective of this paper is to increase the understanding of what role power-to-heat could have in Sweden and to contribute to the development of methods and tools that can be applied when analysing the potential of power-to-heat. For that purpose we estimate the technical potential of power-to-heat for different power scenarios and assumptions and identify key parameters which have significant impact on the potential. The calculations are based on hourly simulations of electricity production, electricity consumption and district heat load. The power-to-heat potential was estimated to 0.2-8.6 TWh, where the potentials at the higher end pertain to scenarios with high amounts of wind and solar power production (corresponding to 54-64% of electricity consumption). Access to thermal storage increases the potential of power-to-heat while the use of industrial waste heat and heat from waste incineration in the district heat load reduces the potential.
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| 2. |
- Zhao, Xin, 1986, et al.
(författare)
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Off-design performance analysis of hybridised aircraft gas turbine
- 2019
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Ingår i: Aeronautical Journal. - : Cambridge University Press (CUP). - 0001-9240 .- 2059-6464. ; 123:1270, s. 1999-2018
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Tidskriftsartikel (refereegranskat)abstract
- An advanced geared turbofan with year 2035 technology level assumptions was established and used for the hybridisation study in this paper. By boosting the low-speed shaft of the turbofan with electrical power through the accessory gearbox, a parallel hybrid concept was set up. Focusing on the off-design performance of the hybridised gas turbine, electrical power input to the shaft, defined as positive hybridisation in this context, generally moves the compressor operation towards surge. On the other hand, the negative hybridisation, which is to reverse the power flow direction can improve the part-load operations of the turbofan and minimise the use of compressor handling bleeds. For the pre-defined mission given in the paper, negative hybridisation of descent, approach and landing, and taxi operations with 580 kW, 240 kW and 650 kW, respectively was found sufficient to keep a minimum compressor surge margin requirement without handling bleed. Looking at the hybridisation of key operating points, boosting the cruise operation of the baseline geared turbofan is, however, detrimental to the engine efficiency as it is pushing the cruise operation further away from the energy optimal design point. Without major modifications to the engine design, the benefit of the hybridisation appears primarily at the thermomechanical design point, the hot-day take-off. With the constraint of the turbine blade metal temperature in mind, a 500kW positive hybridisation at hot-day take-off gave cruise specific fuel consumption (SFC) reduction up to 0.5%, mainly because of reduced cooling flow requirement. Through the introduction of typical electrical power system performance characteristics and engine performance exchange rates, a first principles assessment is illustrated. By applying the strategies discussed in the paper, a 3% reduction in block fuel burn can be expected, if a higher power density electrical power system can be achieved.
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