Appendix Appendix Literature on Flexibility Options The focus of this study is, as mentioned, framework conditions affecting the terms for P2H, CHP and heat storage technologies. The purpose is not a full review of flexibility measures, as this has been provided by others already, e.g. Lund et al. (Lund et al. 2015). Instead, this section deals with a description of selected flexibility options identified from previous studies of the Nordic and Baltic countries. 52 Heat Pumps along with Flexible Cogeneration and Heat Storages As indicated in the introduction, an increasing share of variable renewable energy supply increases the need for flexibility in the energy system. There is a great potential for additional power system flexibility in the production and use of heat, greater than for electric vehicles and electric storage options (Kiviluoma & Meibom 2010). Studies however show that the most effective flexibility option within the DH sector is a combination of several flexibility options, where distributed cogeneration with a thermal storage and an electricity to heat option seems to be the most efficient solution (Lund & Münster 2003). Blarke & Lund (2008) shows that a combination of CHP, heat pumps and cold storage is the most efficient flexibility option. Hvelplund (2006) suggests heat pumps along with flexible cogeneration a better option than increased transmission capacity in Denmark. Hagos et al. (2014) argues that heat pumps together with an increased bio share in heating, as a replacement for direct electric heating, is an economical feasible option to increase flexibility in the Norwegian energy system rather than increasing bio-heating deployment alone. Finland and Sweden have a high share of nuclear power. Zakeri et al. (2015) shows that a high share of nuclear energy limits the integration of electricity from wind, and that there is a need for additional flexibility in such systems. He shows that large heat pumps in connection with a thermal storage, CHP and DH systems offer the highest efficiency in balancing excess power from VRE. However, P2H options offer a limited capability for absorbing excess power, as oversupply arises mainly in the periods with relatively low demand for heat. This calls for longer-term energy storage and/or other flexibility options to achieve a higher renewable share (Zakeri et al. 2015). Storage Capacity Energy can both be stored as electricity and as heat. Battery storages for electricity are very flexible, but are also the most expensive storage option. This advocates for less costly heat storages in the DH sector (Østergaard 2012). Schulz et al. (2013) shows that the benefits of heat storage investments increases with fluctuating electricity prices. Rolfsman (2004) argues that heat storages can contribute to maximizing the electricity generation of CHP plants during peak-price periods, and shows that the investment potential in heat storage tanks increases along with fluctuating electricity prices. Seasonal storages, however, requires sufficient space due to large volume; something which is not always available due to dense population or other geographic limitations. Spatial distribution can mitigate this problem.
WP2 DH report
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