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Low energy buildings equipped with heat pumps for high self-consumption of photovoltaic electricity
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-8287-8735
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The building sector is a prioritized area in the European Unions (EU) ambition to reduce the total final energy use by 20 %; lower the emission of greenhouse gases by 20 % and using energy 20 % more efficient by 2020. The residential sector in the European Union accounts for 27% of the un-ion’s final energy use and the EU views decentralized energy generation and heat pumps as important measures in reducing the energy demand in the building sector.

In recent years a rapid decrease in photovoltaic system prices has led to a growing popularity in Sweden. This fact in combination with a large in-crease of heat pump systems in residential buildings the last decade makes a combination of heat pumps and solar energy systems an interesting sys-tem configuration to analyze. In addition, the electricity price structure in Sweden and the uncertainty of the sustainability of the Swedish solar energy support schemes makes the topic of self-consumption an important research area.

Different solar energy systems for residential buildings and two different storage technologies, batteries and hot water storage tanks, have been analyzed with regards to profitability, solar energy fraction and self-consumption levels.

The results suggest that the system with a heat pump in combination with a photovoltaic system can be profitable and have high solar energy fractions and high levels of self-consumption and that the systems with storage are not profitable but give high levels of self-consumption and relatively high solar energy fractions. The hot water storage gives almost as high level of self-consumption as batteries but have half of the batteries levelized cost of electricity.

A system with a ground source heat pump and a solar thermal system are ineffective, unprofitable and give low solar energy fractions.

A system with a weather forecast controller gives a small increase in self-consumption and is unprofitable.

The proposed near energy zero building definition proposed by the Swedish National Board of Housing, Building and Planning in 2015 is unclear in terms of what electrical load the PV electricity reduces in the building. This has a fairly large impact on the building specific energy demand.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2016. , 59 p.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 200
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-31314ISBN: 978-91-7485-255-4 (print)OAI: oai:DiVA.org:mdh-31314DiVA: diva2:912835
Public defence
2016-04-29, Delta, Mälardalens högskola, Västerås, 09:15 (English)
Opponent
Supervisors
Available from: 2016-03-18 Created: 2016-03-18 Last updated: 2016-04-04Bibliographically approved
List of papers
1. Economic and energy analysis of three solar assisted heat pump systems in near zero energy buildings
Open this publication in new window or tab >>Economic and energy analysis of three solar assisted heat pump systems in near zero energy buildings
2013 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 66, 77-87 p.Article in journal (Refereed) Published
Abstract [en]

The European Union's directive of the energy performance of buildings makes energy systems with local energy generation interesting. To support local energy generation the government has appointed a commission to investigate the possibility to implement net metering for grid connected PV-systems. In this paper three different systems are simulated and analyzed with regards to economics and energy: a PV-system and a heat pump (alternative 1), a heat pump and a solar thermal system (alternative 2) and a heat pump, a PV-system and a solar thermal system (alternative 3). System alternative 1 is profitable with daily net metering and monthly net metering and unprofitable with instantaneous net metering. The solar electrical fraction of the system is 21.5%, 43.5% and 50%, respectively. System alternative 2 is unprofitable and has a solar electricity fraction of 5.7%. System alternative 3 is unprofitable and has a solar electricity fraction of just below 50. The conclusion is that a PV system in combination with a heat pump is a superior alternative to a solar thermal system in combination with a heat pump.

Keyword
Energy system simulation, Ground source heat pump, Near zero energy building, Photovoltaics, Solar collector
National Category
Social Sciences
Identifiers
urn:nbn:se:mdh:diva-21197 (URN)10.1016/j.enbuild.2013.07.042 (DOI)000327904200009 ()2-s2.0-84881521779 (Scopus ID)
Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2017-12-06Bibliographically approved
2. Simulation and analysis of a solar assisted heat pump system with two different storage types for high levels of PV electricity self-consumption
Open this publication in new window or tab >>Simulation and analysis of a solar assisted heat pump system with two different storage types for high levels of PV electricity self-consumption
2014 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 103, no May 2014, 19-27 p.Article in journal (Refereed) Published
Abstract [en]

The incentives for PV-systems in Europe is being gradually lowered or ended. This makes a higher level of self-consumption interesting for owners of PV-systems.Sweden has an incentive of 35% of the investment cost for PV-systems. Unfortunately not all consumers can get this incentive. Therefore a high level of self-consumption will be necessary if the PV-systems are to be profitable in Sweden.A reference system with two different energy storage technologies is investigated in this paper. One system with 48. kW. h of batteries and one system with a hot water storage tank where the electricity is stored as heat.The research questions in this paper are:. Which storage system gives the highest level of PV electricity self-consumption?Are the storage systems profitable with the assumptions made in this paper?What are the levelized costs of electricity (LCOE) for the reference system with different storage system?The system with batteries has a self-consumption of 89% of the annual PV-electricity output and the system with a hot water storage tank has 88%.The system with batteries has a levelized cost of electricity two times higher than the system with a hot water storage tank.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Photovoltaic; Energy storage systems; Energy system simulation; Self-consumption
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-24597 (URN)10.1016/j.solener.2014.02.013 (DOI)000336351800003 ()2-s2.0-84896866196 (Scopus ID)
Funder
Swedish Energy Agency
Available from: 2014-03-06 Created: 2014-03-06 Last updated: 2017-12-05Bibliographically approved
3. Simulation of a proposed novel weather forecast control for ground source heat pumps as a mean to evaluate the feasibility of forecast controls’ influence on the photovoltaic electricity self-consumption
Open this publication in new window or tab >>Simulation of a proposed novel weather forecast control for ground source heat pumps as a mean to evaluate the feasibility of forecast controls’ influence on the photovoltaic electricity self-consumption
2016 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 164, 579-589 p.Article in journal (Refereed) Published
Abstract [en]

The building sector in Europe and Sweden accounts for a large part of the total European electricity end use. A large fraction of Swedish buildings are equipped with heat pumps for heating and a combination of heat pumps and decentralized energy generation from photovoltaic systems is an interesting system solution for reducing the energy use. It is important that the building has a high self-consumption of the generated PV-electricity. Self-consumption can be seen as energy conservation and has a considerable higher economic value than exported electricity for the building owner.

A ground source heat pump with a novel weather forecast controller is simulated in Trnsys and compared to a reference case in regards to self-consumption and profitability. The economic analysis is based on the annuity method and a sensitivity analysis regarding annual cost, discount rate and annual electricity price change has been performed.

The results indicates that the increase in self-consumed photovoltaic electricity is limited to 7% with the proposed novel weather forecast controller, which means that the controller is unprofitable. Because of this the proposed novel forecast controller is not a viable way of increasing self-consumption in systems with photovoltaic systems and ground source heat pumps in Sweden.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Photovoltaic, Weather forecast control, Self-consumption, Ground source heat pump
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-30676 (URN)10.1016/j.apenergy.2015.12.013 (DOI)000372379700053 ()2-s2.0-84950996224 (Scopus ID)
Funder
Swedish Energy Agency
Available from: 2016-01-04 Created: 2016-01-04 Last updated: 2017-12-01Bibliographically approved
4. An analysis on how the proposed Swedish requirements for near zero energy buildings manages PV electricity in combination with two different types of heat pumps.
Open this publication in new window or tab >>An analysis on how the proposed Swedish requirements for near zero energy buildings manages PV electricity in combination with two different types of heat pumps.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This paper presents an in-depth analysis on how exhaust air- and ground source- heat pumps in combination with PV-systems affects the specific energy demand of buildings with the proposed new Swedish near zero energy building definition. It also present a method on how to estimate the contribution from the photovoltaic-system on the reduction of the specific energy demand of the building.

A challenge with the proposed near zero energy building definition is that it is not clearly defined how it manages photovoltaic electricity as a mean to reduce the specific energy demand of buildings. The size of the specific energy demand reduction is, amongst other things, depending on the number of loads in the building and in which assumed sequence the different loads utilizes the photovoltaic electricity.

The results suggest that the building with the ground source heat pump has the lowest specific energy demand. In terms of self-consumption fraction the two heat pump types is fairly equal but the ground source heat pump has a larger solar energy fraction.

The difference between the two photovoltaic electricity usage assumptions used in this article is 6 kWh/m2 for both the GSHP and EAHP Buildings.

Keyword
Heat pump; photovoltaics; near zero energy building; self-consumption
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-31311 (URN)
Funder
Swedish Energy Agency
Available from: 2016-03-18 Created: 2016-03-18 Last updated: 2016-04-07Bibliographically approved

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