| 1. |
- Monie, Svante, 1972-, et al.
(författare)
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A residential community-level virtual power plant to balance variable renewable power generation in Sweden
- 2020
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Power systems with large shares of variable renewable electricity generation, i.e., wind and solar power, require high flexibility in both power generation and demand. Heat pumps and combined heat and power units within district heating systems and thermal storages have previously been studied for their potential to increase the flexibility of the energy system. When using these technologies for power balancing, they must be operated in a non-standard way with switched merit-order. This study hypothesizes that a residential area could form a locally operated entity, i.e., a virtual power plant, that provides power-balancing services to a national power system. The hypothesis is tested with a case study in Sweden where a combined heat and power unit, heat pumps, a local heat distribution system, and thermal storage constitute the local entity. A simulation of the energy balances in the system, with optimization of storage size, was performed. The results show that all power surpluses in the system are consumed by the heat pumps. 43% of the annual and 21% of the electricity peak load are covered by the combined heat and power unit. It is concluded that inter-seasonal thermal storage is crucial for the system’s flexibility. Also, large electricity surpluses, if converted to heat and stored, limit the ability of the virtual power plant to utilize the combined heat and power unit for power balancing at a later stage. Despite this, a local virtual power plant can provide increased flexibility by offering power-balancing services to the power system.
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| 2. |
- Monie, Svante, 1972-
(författare)
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Balancing variable renewable electricity generation using combined heat and power plants, large-scale heat pumps, and thermal energy storages in Swedish district heating systems
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The global ambitions to hamper the greenhouse effect has led to ambitious targets for increasing renewable energy use. This, in combination with recent years' vast development of wind and solar power, implies that there will be significant amounts of variable renewable electricity (VRE) in future energy systems. With the inherent variability in VRE production comes a need for increased contingency in power systems. This requires both controllable production and consumption of power to cope with VRE deficits and surpluses. The purpose of this doctoral thesis is to investigate the potential for providing such power balancing services from Swedish district heating systems (DHS). Analyses are made for different system levels: community, regional, and national. Computer simulations of DH production systems with combined heat and power (CHP) plants, heat pumps, and thermal energy storage (TES), operated to supply a power balancing demand, are here shown to potentially reduce VRE deficits and surpluses. The results further show that reducing peak deficits and/or surpluses mainly depends on the installed capacities in CHP units and/or heat pumps. However, annual deficits or surpluses are reduced more if the system includes a TES. Also, the shares of wind and solar power in VRE mixes are shown to be relevant for fuel use and system performance. Solar-dominated VRE promotes heat pumps, reduces fuel use in CHP, and motivates a seasonal operation of TESs. Wind-dominated VRE matches with high capacities in CHP units, yields increased fuel use and motivates short-term operation of TESs. A crucial limitation is competition for the heat load between heat pumps and CHP units, which reduces the potential for CHP production. Competition between stored heat and heat pumps also occurs in systems with smaller TESs and large amounts of surplus electricity. In order for power balancing services to be economically viable for DHS operators, changed market structures that appropriately value the delivered services are likely required. The overall conclusions are: DHSs can offer power balancing, a high share of PV is essential to reduce fuel use, and finally, seasonal TESs are needed to cope with large amounts of surplus heat and/or replacement of peak load units.
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| 3. |
- Monie, Svante, 1972-, et al.
(författare)
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Comparing electricity balancing capacity, emissions, and cost for three different storage-based local energy systems
- 2020
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Ingår i: IET Renewable Power Generation. - : Institution of Engineering and Technology (IET). - 1752-1416 .- 1752-1424. ; 14:19, s. 3936-3945
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Tidskriftsartikel (refereegranskat)abstract
- This study provides an analysis of the potential for a sub-energy system to provide an electricity balancing service to, in this case, a national energy system with a large share of variable renewable electricity generation. By comparing electricity balancing capacity, CO2, eq-emissions, and costs, three different local residential energy system setups are assessed. The setups contain different combinations of district heating, combined heat and power, thermal energy storage, electric battery storage, heat pumps, and electric boilers. The analysis focuses on system-level integration, heat and electricity cross-sectoral operations, and unconventional production strategies for district heating production. The results show that local sub-energy systems with heat pumps, combined heat and power, and thermal energy storage has the potential to reduce national electricity balancing demand in an economically feasible way, and with modest CO2, eq-emissions. It was also shown that electricity-based heat production without district heating is economically unfavourable, even in the most optimistic scenario; it is not likely to be feasible within a 30-year period.
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| 4. |
- Monie, Svante, 1972-, et al.
(författare)
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Electricity balancing capacity, emissions, and cost comparison of three storage-based local energy systems for variable power generation
- 2019
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Ingår i: 9th International Workshop on Integration of Solar Power and Storage into Power Systems.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study compares three energy system setups for supplying the electricity and heat demand in a residential area. Two of the setups contain district heating and a combined heat and power unit. The first setup contains a thermal storage and the second contains an electric battery. The third setup is all electric (incl. the heat production). The second setup reduced the electricity balancing demand the most, but had the highest CO2,eq-emissions. The third setup had no emissions, but the highest cost. This setup also increased the balancing demand. The first system, with the thermal storage, performed most satisfying when electricity balancing capacity, CO2,eq-emissions, and costs were weighed together.
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| 5. |
- Monie, Svante, 1972-, et al.
(författare)
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Potential for existing rock caverns in Sweden to be used as flexible district heating loads to alleviate the inherent net load variability from renewable energy
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Large shares of variable renewable electricity (VRE) generation increase the demand for flexible power balancing capacities for handling both power surpluses and deficits. Within district heating (DH) production systems, electricity can be produced in combined heat and power plants, as well consumed in for example heat pumps. However, the power balancing (electricity production and consumption) potentials for DH production units are limited by the varying level of heat load. To improve these potentials, large-scale thermal energy storages (TES) can be used to increase heat-load flexibility. In Sweden, former rock cavern oil depots exist that can be converted to TESs. This study investigates the power balancing capacity of 58 DH systems with access to rock cavern TESs. A power balancing production strategy is applied for the heat and electricity production in the systems. The results show that Swedish DH, on a national scale, and with 60% wind power and 10% photovoltaic power covering the national load, potentially could reduce VRE power deficits by 9% and surpluses by 12%. Also, the results show that there will be competition for the heat load between heat pumps and CHP units. The fuel used in DH production is reduced by approximately 10%. The study highlights the impact of the temporal distribution and the annual shares of VRE sur-pluses and deficits on fuel use.
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| 6. |
- Monie, Svante, 1972-, et al.
(författare)
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Potential for existing rock caverns in Sweden to be used as flexible district heating loads to alleviate the inherent net load variability from renewable energy
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Large shares of variable renewable electricity (VRE) generation increase the demand for flexible power balancing capacities for handling both power surpluses and deficits. Within district heating (DH) production systems, electricity can be produced in combined heat and power plants, as well consumed in for example heat pumps. However, the power balancing (electricity production and consumption) potentials for DH production units are limited by the varying level of heat load. To improve these potentials, large-scale thermal energy storages (TES) can be used to increase heat-load flexibility. In Sweden, former rock cavern oil depots exist that can be converted to TESs. This study investigates the power balancing capacity of 58 DH systems with access to rock cavern TESs. A power balancing production strategy is applied for the heat and electricity production in the systems. The results show that Swedish DH, on a national scale, and with 60% wind power and 10% photovoltaic power covering the national load, potentially could reduce VRE power deficits by 9% and surpluses by 12%. Also, the results show that there will be competition for the heat load between heat pumps and CHP units. The fuel used in DH production is reduced by approximately 10%. The study highlights the impact of the temporal distribution and the annual shares of VRE sur-pluses and deficits on fuel use.
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| 7. |
- Monie, Svante, 1972-, et al.
(författare)
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Power balancing capacity and biomass demand from flexible district heating production to balance variable renewable power generation
- 2021
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Ingår i: Smart Energy. - : Elsevier. - 2666-9552. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The European Commission has, following the Paris Agreement, announced a “European Green Deal” to decarbonize energy sectors and increase renewable power. This study investigates to what extent district heating systems with biomass-fueled combined heat and power, electricity-driven compression heat pumps, and pit thermal energy storages, can contribute to power balancing capacity in a future Swedish power system with a high share of variable renewable electricity production. District heat production is, in this study, unconventionally controlled to primarily supply a power balancing demand, where co-produced heat is stored if not directly supplied to district heating users. The impact of this on biomass demand is also investigated. Simulations are made on an aggregated level for one part of the Swedish electricity market. The results show that district heating systems have the potential to reduce peak variable renewable power deficits by up to 52%. All power surpluses can potentially be used for heat production in heat pumps. A heat storage capacity of 17-18% of the heat demand is necessary. Fuel use is 11-12% higher for district heating production controlled for power balancing compared to conventional heat production, depending on the mix of renewable power generation technologies. For instance, a large share of solar power in relation to wind power reduces fuel use to a greater extent when compared to the opposite relation.
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| 8. |
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| 9. |
- Monie, Svante, 1972-, et al.
(författare)
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Power-to-heat on the reserve capacity market-Policy implications considering economic constraints and competing heat production
- 2022
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- Studies have shown that surplus power from variable renewable electricity generation can be consumed in electric boilers or compressor heat pumps, i.e., Power-to-Heat (P2H), for heat production. This potentially provides power balancing for the electric grid and can also decarbonize and/or reduce biofuel demand in the district heating (DH) sector. This sector-coupling of thermal and electrical systems is, how-ever, limited by production planning complexity, grid fees, tariffs, and risk-averse actors. The conditions for P2H production vary between DH-systems due to non-homogeneity in the configuration of production units in different systems. This study investigates the economic feasibility of placing bids for P2H electricity consumption on the reserve capacity market in three different DH systems. It is assumed that P2H electricity consumption is controlled by a hypothetical balance operator. To increase production flexibility, the DH systems are equipped with heat storage where P2H-produced heat is stored. The results show that P2H on the reserve capacity market can increase revenue for DH operators, but DH systems with co-generation of heat and electricity risk reducing income from power production. Furthermore, stored heat needs to compete with cost-efficient base-load production to avoid the large storage required. The power balancing potential of P2H in DH systems is generally limited by the installed P2H capacity as well as the rest of the constituents and the production strategy of the DH system. To overcome these limitations, policies are needed that reward power balancing services and provide investment support for P2H capacity and heat storage. Published under an exclusive license by AIP Publishing.
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| 10. |
- Monie, Svante, 1972-, et al.
(författare)
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Thermal Energy Storages in Residential Areas : – a potential to increase renewable power generation?
- 2018
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Ingår i: 2018 ACEEE Summer Study on Energy Efficiency in Buildings. - Washington D.C.. ; , s. 11-1-11-12
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Konferensbidrag (refereegranskat)abstract
- With an increased ambition of implementing renewable electricity production in our energy systems follows the need of handling the inherent variability from some of these production sources (e.g. wind and solar). This could be via curtailments, infrastructural reinforcements of the power grid, and/or increased utilization of power system reserves. The aim of this study was to investigate if power surplus and deficit due to mismatch between intermittent power generation and power demand could be reduced with electric heat pumps (used for power-to-heat purposes), combined heat and power (CHP) production (for power balancing), and seasonal thermal energy storage (STES) (as buffering capacity). A residential area consisting of buildings refurbished for improved energy performance, roof top solar photovoltaic (PV) systems, a local heat distribution system, a small-scale CHP plant, central heat pumps, and a STES, was simulated. The heat pumps were given priority to use surplus power from roof top PV generation or surplus from the grid (e.g. wind power). The CHP plant produced power during power deficits. Surplus heat from the CHP plant as well as from the heat pumps was stored in the STES. The results showed a reduction of the surplus power from the local PV systems towards the upstream power grid. Also, the possibility to offer regulative service towards upstream power grid by using CHP was demonstrated. The conclusion is that power-to-heat and CHP can significantly reduce the mismatch between variable power generation and power demand.
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