Janne Hirvonen - Academia.edu (original) (raw)

Papers by Janne Hirvonen

Buildings

To achieve carbon neutrality in the EU, it is important to renovate the existing EU residential b... more To achieve carbon neutrality in the EU, it is important to renovate the existing EU residential buildings for a higher building energy efficiency. This study examines the impacts of several novel renovation technologies on energy consumption, CO2 emissions and indoor climates in southern European residential buildings through building-level simulations. Three typical residential buildings in South Europe were chosen as the demo buildings to implement the novel technologies. The technologies were classified into passive, ventilation and generation packages, and then simulated independently under the intermittent and continuous heating schedules. Additionally, two final combinations of renovation technologies were also simulated to demonstrate the maximum energy and CO2 emissions reduction potential of the demo buildings. All novel retrofit technologies manifested obvious effects on the energy consumption and CO2 emissions. Nevertheless, the effects were significantly affected by the ...

Tämä raportti käsittää hukkalämpöjen hyödyntämisen nykytilanteen ja kehitysnäkymät, HUKATON-hankk... more Tämä raportti käsittää hukkalämpöjen hyödyntämisen nykytilanteen ja kehitysnäkymät, HUKATON-hankkeen tarkastelukohteiden simulointi- ja yhteiskehittämistyön tulokset, laajan liiketoiminnan kyselyn ja selvityksen liiketoiminnan näkymistä sekä suositukset tarkastelukohteisiin ja liiketoiminnan edistämiseen. Hankkeessa tutkittiin ja kehitettiin yhteensä kuutta kohdetta, joista kaksi on Helsingin kaupungin omistuksessa ja neljä yksityisomistuksessa Turun seudulla. Helsingin tarkastelukohteet valittiin yhteispäätöksellä, jonka tekoon osallistuivat asiantuntijat Helsingin kaupungin ympäristötiimistä, Heleniltä ja Aalto-yliopistosta. HUKATON-hankkeen päätavoitteena oli kehittää optimointilaskentaan ja yhteiskehittämiseen pohjautuvia uusia hukkalämmön talteenottoon perustuvia kokonaisratkaisuja, jotka tuovat rakennukset osaksi älykästä energiajärjestelmää kulutusjouston näkökulmasta. HUKATON-hankkeen tavoitteena oli lisäksi tuoda markkinoille täysin uusia digitaalisuuteen perustuvia palvelu...

Buildings, 2020

In countries with high heating demand, waste heat from industrial processes should be carefully u... more In countries with high heating demand, waste heat from industrial processes should be carefully utilized in buildings. Finland already has an extensive district heating grid and large amounts of combined heat and power generation. However, despite the average climate, there is little use for excess heat in summer. Waste incineration plants need to be running regardless of weather, so long-term storage of heat requires consideration. However, no seasonal energy storage systems are currently in operation in connection with Finnish waste incineration plants. This study used dynamic energy simulation performed with the TRNSYS 17 software to analyze the case of utilizing excess heat from waste incineration to supplement conventional district heating of a new residential area. Seasonal energy storage was utilized through a borehole thermal energy storage (BTES) system. Parametric runs using 36 different storage configurations were performed to find out the cost and performance range of su...

Energies, 2020

This study examines how the energy renovation of old detached houses affects the hourly power con... more This study examines how the energy renovation of old detached houses affects the hourly power consumption of heating and electricity in Finland. As electrification of heating through heat pumps becomes more common, the effects on the grid need to be quantified. Increased fluctuation and peak power demand could increase the need for fossil-based peaking power plants or call for new investments to the distribution infrastructure. The novelty in this study is the focus on hourly power demand instead of just annual energy consumption. Identifying the influence of building energy retrofits on the instantaneous power demand can help guide policy and investments into building retrofits and related technology. The work was done through dynamic building simulation and utilized building configurations obtained through multi-objective optimization. Deep energy retrofits decreased both the total and peak heating power consumption. However, the use of air-source heat pumps increased the peak pow...

Proceedings of SWC2017/SHC2017, 2017

There is a need to accelerate the application of advanced clean energy technologies to resolve th... more There is a need to accelerate the application of advanced clean energy technologies to resolve the challenges of climate change. Solar heating is a feasible solution among clean energy technologies. These technologies are not yet highly used in high latitudes due to various challenges. This paper focuses on the community sized solar district heating system configuration for cold climates. The proposed configuration consists of a partially decentralized heating system. Each individual house heat pump was connected between large centralized solarcharged low temperature tank and smaller decentralized individual high temperature tank in each house. Additionally, the large centralized tank was directly charged by solar-charged borehole storage during winters. Dynamic simulation approach was used through TRNSYS software coupled with MOBO (multi-objective building optimizer) for NSGA-II optimization algorithm. The purchased electricity and investments were two objectives minimized. The impact of the energy system on the renewable energy fraction, purchased electricity and investments as a function of the building heating demand, collectors and photovoltaic areas, short-term tanks storages and boreholes volumes were evaluated. Results showed that purchased electricity varied 47 kWh/m 2 /yr-25 kWh/m 2 /yr and renewable energy fraction 75%-91%.

E3S Web of Conferences, 2021

Most Finnish residential buildings have been built before ventilation heat recovery options becam... more Most Finnish residential buildings have been built before ventilation heat recovery options became mandatory. Exhaust air heat pumps are an effective way to reduce emissions, but they cannot cover all heating demand. Ground-source heat pumps can be designed to meet all loads, but they require corresponding amounts of space both above and below ground. This simulation study combines residential ventilation and sewage waste heat with a ground-source heat pump system to improve system sustainability and cost-effectiveness. A hybrid waste heat and ground-source heat pump system was shown to have 20% lower life cycle costs compared to a pure ground-source heat pump system. It also maintained sustainable ground temperature levels over the long term, while reducing above-ground space requirements by 95%.

Sustainable Cities and Society, 2021

Finland and the European Union aim to reduce CO 2 emissions by 80-100 % before 2050. This require... more Finland and the European Union aim to reduce CO 2 emissions by 80-100 % before 2050. This requires drastic changes in all emissions-generating sectors. In the building sector, all new buildings are required to be nearly zero energy buildings. However, 79 % of buildings in Finland were built before 2000, meaning that they lack heat recovery and suffer from badly insulated facades. This study presents four large-scale building energy retrofit scenarios, showing the emission reduction potential in the whole Finnish building stock. Six basic building types with several age categories and heating systems were used to model the energy demand in the building stock. Retrofitted building configurations were chosen using simulation-based multi-objective optimisation and combined according to a novel building stock model. After large-scale building retrofits, the national district heating demand was reduced by 25-63 % compared to the business as usual development scenario. Despite a large increase in the number of heat pumps in the system, retrofits in buildings with direct electric heating can prevent the rise of national electricity consumption. CO 2 emissions in the different scenarios were reduced by 50-75 % by 2050 using current emissions factors.

Energies, 2020

In Finland, old apartments (1980s) contribute toward emissions. The objective is to reduce CO2 em... more In Finland, old apartments (1980s) contribute toward emissions. The objective is to reduce CO2 emissions to reach Europe’s targets of 2050. Three different centralized solar-based district heating systems integrated either with non-renovated or renovated old buildings in the community were simulated and compared against the reference city-level district heating system. The three proposed centralized systems were: Case 1: photovoltaic (PV) with a ground source heat pump (GSHP); Case 2: PV with an air-water heat pump (A2WHP); and Case 3: PV with A2WHPs, seasonal storage, and GSHPs. TRNSYS simulation software was used for dynamic simulation of the systems. Life cycle cost (LCC), CO2 emissions and purchased electricity were calculated and compared. The results show that the community-level district heating system (Case 3) outperformed Case 1, Case 2, and the city-level district heating. With non-renovated buildings, the relative emissions reduction was 83% when the reference energy syst...

Buildings, 2020

Energy retrofitting of buildings shows great potential in reducing CO2 emissions. However, most r... more Energy retrofitting of buildings shows great potential in reducing CO2 emissions. However, most retrofitting studies only focus on a single building type. This paper shows the relative potential in six Finnish building types, to identify possible focus areas for future retrofits in Finland. Data from previous optimization studies was used to provide optimal cases for comparison. Energy demand of the buildings was generated through dynamic simulation with the IDA-ICE software. The cases were compared according to emissions reduction, investment and life cycle cost. It was found that, in all buildings, it was possible to reduce emissions cost-neutrally by 20% to 70% in buildings with district heating and by 70% to 95% using heat pumps. Single-family homes with oil or wood boilers switching to heat pumps had the greatest emission reduction potential. More stringent requirements for energy efficiency could be mandated during building renovation.

Processes, 2020

In the pursuit of mitigating the effects of climate change the European Union and the government ... more In the pursuit of mitigating the effects of climate change the European Union and the government of Finland have set targets for emission reductions for the near future. This study examined the carbon emission reduction potential in the Finnish energy system with power-to-heat (P2H) coupling of the electricity and heat sectors with different housing renovation levels. The measures conducted in the energy system were conducted as follows. Wind power generation was increased in the Finnish power system with 10 increments. For each of these, the operation of hydropower was optimized to maximize the utilization of new wind generation. The excess wind generation was used to replace electricity and heat from combined heat and power production for district heating. The P2H conversion was performed by either 2000 m deep borehole heat exchangers coupled to heat pumps, with possible priming of heat, or with electrode boilers. The housing stock renovated to different levels affected both the e...

Energies, 2019

To mitigate the effects of climate change, the European Union calls for major carbon emission red... more To mitigate the effects of climate change, the European Union calls for major carbon emission reductions in the building sector through a deep renovation of the existing building stock. This study examines the cost-effective energy retrofit measures in Finnish detached houses. The Finnish detached house building stock was divided into four age classes according to the building code in effect at the time of their construction. Multi-objective optimization with a genetic algorithm was used to minimize the life cycle cost and CO2 emissions in each building type for five different main heating systems (district heating, wood/oil boiler, direct electric heating, and ground-source heat pump) by improving the building envelope and systems. Cost-effective emission reductions were possible with all heating systems, but especially with ground-source heat pumps. Replacing oil boilers with ground-source heat pumps (GSHPs), emissions could be reduced by 79% to 92% across all the studied detached...

E3S Web of Conferences, 2019

This study examined the cost-optimality of energy renovation on Finnish apartment buildings of di... more This study examined the cost-optimality of energy renovation on Finnish apartment buildings of different ages, built according to different energy performance requirements. Multi-objective optimization was utilized to minimize both CO2 emissions and life cycle cost (LCC). IDA-ICE simulations were performed to obtain the hourly heating demand of the buildings. Four building age classes and three heating systems (district heating, exhaust air heat pump and ground-source heat pump) were separately optimized. With district heating, it was possible to reduce emissions by 11%, while also reducing LCC. With heat pumps cost-savings could be achieved while reducing emissions by over 49%. With maximal (not cost-effective) investments, emissions could be reduced by more than 70% in all examined cases. In all cases, the cheapest solutions included solar electricity and sewage heat recovery. In old buildings, window upgrades and additional roof insulation were cost-effective. In new buildings, d...

Energies, 2019

Demand response has been studied in district heating connected buildings since the rollout of sma... more Demand response has been studied in district heating connected buildings since the rollout of smart, communicating devices has made it cost-effective to control buildings’ energy consumption externally. This research investigates optimal demand response control strategies from the district heating operator perspective. Based on earlier simulations on the building level, different case algorithms were simulated on a typical district heating system. The results show that even in the best case, heat production costs can be decreased by only 0.7%. However, by implementing hot water thermal storage in the system, demand response can become more profitable, resulting in 1.4% cost savings. It is concluded that the hot water storage tank can balance district heating peak loads for longer periods of time, which enhances the ability to use demand response strategies on a larger share of the building stock.

International Journal of Sustainable Energy, 2019

Effect of apartment building energy renovation on hourly power demand Optimal energy renovations ... more Effect of apartment building energy renovation on hourly power demand Optimal energy renovations of apartment buildings in Finland have a great impact on annual energy demand. However, reduction of energy demand does not necessarily translate into similar changes in peak power demand. Four different types of apartment buildings, representing the Finnish apartment building stock, were examined after optimal energy retrofits to see the influence of retrofitting on hourly power demand. Switching from district heating to ground-source heat pumps reduced emissions significantly under current energy mix. However, the use of ground-source heat pumps increased hourly peak electricity demand by 46 to 153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30 to 108% in the peak month of January. This could increase the use of high emission peak power plants and negate some of the emission benefits. Solar thermal collectors and heat recovery systems could reduce purchased heating energy to zero in summer. Solar electricity could reduce median power demand in summer, but had only a little effect on peak power demand. The reduction in peak power demand after energy retrofits was less than the reduction in energy demand.

Energy Conversion and Management, 2019

Climate change is one of the biggest challenges at the present time, and to tackle such issue, so... more Climate change is one of the biggest challenges at the present time, and to tackle such issue, solar energy and efficient buildings, in general, can be used. The goal is to design and optimize photovoltaic based decentralized district heating system and later compare it-economically and technically-against three different optimized typologies of solar district heating system in Nordic conditions. The photovoltaic based decentralized system consists of one centralized low temperature tank charged by photovoltaic and air-water heat pumps and a borehole thermal energy storage, while the decentralized high temperature tank charged by an individual water-water heat pump in each house. The centralized warm tank charges the borehole thermal energy storage. The other three systems are photovoltaic based centralized, roof-mounted solar thermal based centralized and roof-mounted solar thermal based decentralized district heating systems. In solar thermal based systems, collectors are used to directly charge the short-term storage tanks instead of the photovoltaics/heat pump combination. The proposed system is simulated using TRNSYS software. Lastly, purchased electricity and life cycle costs of the system are minimized using multi-objective optimization and the genetic algorithm. The results indicated that the decentralized photovoltaic based system outdoes all the other systems in terms of techno-economic performance. The purchased electricity can be reduced by 22% while at the same time life cycle cost can be reduced up to 40%, compared to the worst optimized system (solar thermal based centralized system). Moreover, the decentralized photovoltaic based energy system has a payback period of 9-27 years, compared to the solar thermal based system and the conventional single building-heat pump system, i.e. around 17-58 years and 15 years, respectively. The highest renewable energy fraction for heating can be close to 99% for this system. The decentralization and electrical based district systems are better in terms of life cycle cost, payback period and in terms of technical performance, compared to traditional single house and solar thermal based district heating systems.

International Journal of Sustainable Energy, 2018

Towards the EU emissions targets of 2050: Optimal energy renovation measures of Finnish apartment... more Towards the EU emissions targets of 2050: Optimal energy renovation measures of Finnish apartment buildings Member countries of the European Union have released targets to reduce carbon dioxide emissions by 80% by the year 2050. Energy use in buildings is a major source of these emissions, which is why this study focused on the cost-optimal renovation of Finnish apartment buildings. Apartment buildings from four

Solar Energy, 2018

A solar community meets a significant amount of its energy demand through solar energy. In a high... more A solar community meets a significant amount of its energy demand through solar energy. In a high latitude country like Finland, the seasonal mismatch of solar availability makes it very difficult to achieve high renewable energy fractions without seasonal storage. In this study, a solar community located in Finland was optimized with respect to energy demand and life cycle cost. To gain better understanding of both technical and economical scaling effects, the optimization was done separately for four cases with 50, 100, 200 and 500 buildings. The study was performed for Finnish conditions using dynamic TRNSYS simulations and optimized with a genetic algorithm, using the MOBO optimization tool. The modeled energy system had solar thermal collectors and solar electric panels for energy generation, two centralized short-term storage tanks and a seasonal borehole thermal energy storage system (BTES) for energy storage, and a ground source heat pump for additional heat generation. The larger communities provided noticeable cost-benefits when aiming for high performance. Larger seasonal storages allowed more direct utilization of seasonally stored heat, lowering the need for the heat pump and reducing electricity demand. Comparing the best and worst performing optimal energy system, annual demand for heating electricity was reduced by 80%. Renewable energy fractions close to 90% for heating were possible for all community sizes, but the large communities could obtain them with about 20% lower costs.

Applied Energy, 2018

Solar thermal energy is widely recognized as one of the most important renewable energy resources... more Solar thermal energy is widely recognized as one of the most important renewable energy resources. However, in high latitudes, due to various climatic and mismatch challenges, such solar district heating networks are difficult to implement. The objective of the paper is to optimize and compare two different design layouts and control strategies for solar district heating systems in Finnish conditions. The two different designs proposed are a centralized and a semidecentralized solar district heating system. The centralized system consists of two centralized short-term tanks operating at different temperature levels charged by a solar collector and heat pumps. Borehole thermal energy storage is also charged via these two centralized tanks. In contrast, the semi-decentralized system consists of one centralized low temperature tank charged by a solar collector and a borehole thermal energy storage and decentralized high temperature tank charged by an individual heat pump in each house. In this case, borehole thermal energy storage is charged only by the centralized warm tank. These systems are designed using the dynamic simulation software TRNSYS for Finnish conditions. Later on, multi-objective optimization is carried out with a genetic algorithm using the MOBO (Multiobjective building optimizer) optimization tool, where two objectives, i.e. purchased electricity and life cycle costs, are minimized. Various design variables are considered, which included both component sizes and control parameters as inputs to the optimization. The optimization results show that in terms of life cycle cost and purchased electricity, the decentralized system clearly outperforms the centralized system. With a similar energy performance, the reduction in life cycle cost is up to 35% for the decentralized system. Both systems can achieve close to 90% renewable energy fraction. These systems are also sensitive to the prices. Furthermore, the results show that the solar thermal collector area and seasonal storage volume can be reduced in a decentralized system to reduce the cost compared to a centralized system. The losses in the centralized system are 40-12% higher compared to the decentralized system. The results also show that in both systems, high performance is achieved when the borehole storage is wider with less depth, as it allows better direct utilization of seasonally stored heat. The system layout and controls varied the performance and life cycle cost; therefore it is essential to consider these when implementing such systems.

Renewable Energy, 2018

Solar energy use in Nordic countries suffers from a high seasonal mismatch of generation and dema... more Solar energy use in Nordic countries suffers from a high seasonal mismatch of generation and demand. However, given a large enough community, seasonal thermal storage could be utilized to store summertime heat gains for use in winter. This simulation study examined a Finnish case of fully electric solar heating, where heat pumps (HP) powered by photovoltaic (PV) panels were used for generating heat for both immediate use and for seasonal storage through a borehole thermal energy storage (BTES) system. Multi-objective optimization of LCC and energy use was performed by a genetic algorithm and TRNSYS simulations. Comparison was done between communities of a 100 and 500 buildings. The need for purchased electricity was between 40 and 26 kWh/m 2 per year for the optimal configurations. For the same cases the life cycle cost was between 220 and 340 V/m 2. Up to 98% renewable energy fraction was obtained for heating, showing that even in Finland it is possible to provide practically all heating by solar energy. The PV-type heating system was also compared to a solar thermal heating system from a previous study and it was found that the new design had as much as 36% lower life cycle cost.

Buildings

To achieve carbon neutrality in the EU, it is important to renovate the existing EU residential b... more To achieve carbon neutrality in the EU, it is important to renovate the existing EU residential buildings for a higher building energy efficiency. This study examines the impacts of several novel renovation technologies on energy consumption, CO2 emissions and indoor climates in southern European residential buildings through building-level simulations. Three typical residential buildings in South Europe were chosen as the demo buildings to implement the novel technologies. The technologies were classified into passive, ventilation and generation packages, and then simulated independently under the intermittent and continuous heating schedules. Additionally, two final combinations of renovation technologies were also simulated to demonstrate the maximum energy and CO2 emissions reduction potential of the demo buildings. All novel retrofit technologies manifested obvious effects on the energy consumption and CO2 emissions. Nevertheless, the effects were significantly affected by the ...

Tämä raportti käsittää hukkalämpöjen hyödyntämisen nykytilanteen ja kehitysnäkymät, HUKATON-hankk... more Tämä raportti käsittää hukkalämpöjen hyödyntämisen nykytilanteen ja kehitysnäkymät, HUKATON-hankkeen tarkastelukohteiden simulointi- ja yhteiskehittämistyön tulokset, laajan liiketoiminnan kyselyn ja selvityksen liiketoiminnan näkymistä sekä suositukset tarkastelukohteisiin ja liiketoiminnan edistämiseen. Hankkeessa tutkittiin ja kehitettiin yhteensä kuutta kohdetta, joista kaksi on Helsingin kaupungin omistuksessa ja neljä yksityisomistuksessa Turun seudulla. Helsingin tarkastelukohteet valittiin yhteispäätöksellä, jonka tekoon osallistuivat asiantuntijat Helsingin kaupungin ympäristötiimistä, Heleniltä ja Aalto-yliopistosta. HUKATON-hankkeen päätavoitteena oli kehittää optimointilaskentaan ja yhteiskehittämiseen pohjautuvia uusia hukkalämmön talteenottoon perustuvia kokonaisratkaisuja, jotka tuovat rakennukset osaksi älykästä energiajärjestelmää kulutusjouston näkökulmasta. HUKATON-hankkeen tavoitteena oli lisäksi tuoda markkinoille täysin uusia digitaalisuuteen perustuvia palvelu...

Buildings, 2020

In countries with high heating demand, waste heat from industrial processes should be carefully u... more In countries with high heating demand, waste heat from industrial processes should be carefully utilized in buildings. Finland already has an extensive district heating grid and large amounts of combined heat and power generation. However, despite the average climate, there is little use for excess heat in summer. Waste incineration plants need to be running regardless of weather, so long-term storage of heat requires consideration. However, no seasonal energy storage systems are currently in operation in connection with Finnish waste incineration plants. This study used dynamic energy simulation performed with the TRNSYS 17 software to analyze the case of utilizing excess heat from waste incineration to supplement conventional district heating of a new residential area. Seasonal energy storage was utilized through a borehole thermal energy storage (BTES) system. Parametric runs using 36 different storage configurations were performed to find out the cost and performance range of su...

Energies, 2020

This study examines how the energy renovation of old detached houses affects the hourly power con... more This study examines how the energy renovation of old detached houses affects the hourly power consumption of heating and electricity in Finland. As electrification of heating through heat pumps becomes more common, the effects on the grid need to be quantified. Increased fluctuation and peak power demand could increase the need for fossil-based peaking power plants or call for new investments to the distribution infrastructure. The novelty in this study is the focus on hourly power demand instead of just annual energy consumption. Identifying the influence of building energy retrofits on the instantaneous power demand can help guide policy and investments into building retrofits and related technology. The work was done through dynamic building simulation and utilized building configurations obtained through multi-objective optimization. Deep energy retrofits decreased both the total and peak heating power consumption. However, the use of air-source heat pumps increased the peak pow...

Proceedings of SWC2017/SHC2017, 2017

There is a need to accelerate the application of advanced clean energy technologies to resolve th... more There is a need to accelerate the application of advanced clean energy technologies to resolve the challenges of climate change. Solar heating is a feasible solution among clean energy technologies. These technologies are not yet highly used in high latitudes due to various challenges. This paper focuses on the community sized solar district heating system configuration for cold climates. The proposed configuration consists of a partially decentralized heating system. Each individual house heat pump was connected between large centralized solarcharged low temperature tank and smaller decentralized individual high temperature tank in each house. Additionally, the large centralized tank was directly charged by solar-charged borehole storage during winters. Dynamic simulation approach was used through TRNSYS software coupled with MOBO (multi-objective building optimizer) for NSGA-II optimization algorithm. The purchased electricity and investments were two objectives minimized. The impact of the energy system on the renewable energy fraction, purchased electricity and investments as a function of the building heating demand, collectors and photovoltaic areas, short-term tanks storages and boreholes volumes were evaluated. Results showed that purchased electricity varied 47 kWh/m 2 /yr-25 kWh/m 2 /yr and renewable energy fraction 75%-91%.

E3S Web of Conferences, 2021

Most Finnish residential buildings have been built before ventilation heat recovery options becam... more Most Finnish residential buildings have been built before ventilation heat recovery options became mandatory. Exhaust air heat pumps are an effective way to reduce emissions, but they cannot cover all heating demand. Ground-source heat pumps can be designed to meet all loads, but they require corresponding amounts of space both above and below ground. This simulation study combines residential ventilation and sewage waste heat with a ground-source heat pump system to improve system sustainability and cost-effectiveness. A hybrid waste heat and ground-source heat pump system was shown to have 20% lower life cycle costs compared to a pure ground-source heat pump system. It also maintained sustainable ground temperature levels over the long term, while reducing above-ground space requirements by 95%.

Sustainable Cities and Society, 2021

Finland and the European Union aim to reduce CO 2 emissions by 80-100 % before 2050. This require... more Finland and the European Union aim to reduce CO 2 emissions by 80-100 % before 2050. This requires drastic changes in all emissions-generating sectors. In the building sector, all new buildings are required to be nearly zero energy buildings. However, 79 % of buildings in Finland were built before 2000, meaning that they lack heat recovery and suffer from badly insulated facades. This study presents four large-scale building energy retrofit scenarios, showing the emission reduction potential in the whole Finnish building stock. Six basic building types with several age categories and heating systems were used to model the energy demand in the building stock. Retrofitted building configurations were chosen using simulation-based multi-objective optimisation and combined according to a novel building stock model. After large-scale building retrofits, the national district heating demand was reduced by 25-63 % compared to the business as usual development scenario. Despite a large increase in the number of heat pumps in the system, retrofits in buildings with direct electric heating can prevent the rise of national electricity consumption. CO 2 emissions in the different scenarios were reduced by 50-75 % by 2050 using current emissions factors.

Energies, 2020

In Finland, old apartments (1980s) contribute toward emissions. The objective is to reduce CO2 em... more In Finland, old apartments (1980s) contribute toward emissions. The objective is to reduce CO2 emissions to reach Europe’s targets of 2050. Three different centralized solar-based district heating systems integrated either with non-renovated or renovated old buildings in the community were simulated and compared against the reference city-level district heating system. The three proposed centralized systems were: Case 1: photovoltaic (PV) with a ground source heat pump (GSHP); Case 2: PV with an air-water heat pump (A2WHP); and Case 3: PV with A2WHPs, seasonal storage, and GSHPs. TRNSYS simulation software was used for dynamic simulation of the systems. Life cycle cost (LCC), CO2 emissions and purchased electricity were calculated and compared. The results show that the community-level district heating system (Case 3) outperformed Case 1, Case 2, and the city-level district heating. With non-renovated buildings, the relative emissions reduction was 83% when the reference energy syst...

Buildings, 2020

Energy retrofitting of buildings shows great potential in reducing CO2 emissions. However, most r... more Energy retrofitting of buildings shows great potential in reducing CO2 emissions. However, most retrofitting studies only focus on a single building type. This paper shows the relative potential in six Finnish building types, to identify possible focus areas for future retrofits in Finland. Data from previous optimization studies was used to provide optimal cases for comparison. Energy demand of the buildings was generated through dynamic simulation with the IDA-ICE software. The cases were compared according to emissions reduction, investment and life cycle cost. It was found that, in all buildings, it was possible to reduce emissions cost-neutrally by 20% to 70% in buildings with district heating and by 70% to 95% using heat pumps. Single-family homes with oil or wood boilers switching to heat pumps had the greatest emission reduction potential. More stringent requirements for energy efficiency could be mandated during building renovation.

Processes, 2020

In the pursuit of mitigating the effects of climate change the European Union and the government ... more In the pursuit of mitigating the effects of climate change the European Union and the government of Finland have set targets for emission reductions for the near future. This study examined the carbon emission reduction potential in the Finnish energy system with power-to-heat (P2H) coupling of the electricity and heat sectors with different housing renovation levels. The measures conducted in the energy system were conducted as follows. Wind power generation was increased in the Finnish power system with 10 increments. For each of these, the operation of hydropower was optimized to maximize the utilization of new wind generation. The excess wind generation was used to replace electricity and heat from combined heat and power production for district heating. The P2H conversion was performed by either 2000 m deep borehole heat exchangers coupled to heat pumps, with possible priming of heat, or with electrode boilers. The housing stock renovated to different levels affected both the e...

Energies, 2019

To mitigate the effects of climate change, the European Union calls for major carbon emission red... more To mitigate the effects of climate change, the European Union calls for major carbon emission reductions in the building sector through a deep renovation of the existing building stock. This study examines the cost-effective energy retrofit measures in Finnish detached houses. The Finnish detached house building stock was divided into four age classes according to the building code in effect at the time of their construction. Multi-objective optimization with a genetic algorithm was used to minimize the life cycle cost and CO2 emissions in each building type for five different main heating systems (district heating, wood/oil boiler, direct electric heating, and ground-source heat pump) by improving the building envelope and systems. Cost-effective emission reductions were possible with all heating systems, but especially with ground-source heat pumps. Replacing oil boilers with ground-source heat pumps (GSHPs), emissions could be reduced by 79% to 92% across all the studied detached...

E3S Web of Conferences, 2019

This study examined the cost-optimality of energy renovation on Finnish apartment buildings of di... more This study examined the cost-optimality of energy renovation on Finnish apartment buildings of different ages, built according to different energy performance requirements. Multi-objective optimization was utilized to minimize both CO2 emissions and life cycle cost (LCC). IDA-ICE simulations were performed to obtain the hourly heating demand of the buildings. Four building age classes and three heating systems (district heating, exhaust air heat pump and ground-source heat pump) were separately optimized. With district heating, it was possible to reduce emissions by 11%, while also reducing LCC. With heat pumps cost-savings could be achieved while reducing emissions by over 49%. With maximal (not cost-effective) investments, emissions could be reduced by more than 70% in all examined cases. In all cases, the cheapest solutions included solar electricity and sewage heat recovery. In old buildings, window upgrades and additional roof insulation were cost-effective. In new buildings, d...

Energies, 2019

Demand response has been studied in district heating connected buildings since the rollout of sma... more Demand response has been studied in district heating connected buildings since the rollout of smart, communicating devices has made it cost-effective to control buildings’ energy consumption externally. This research investigates optimal demand response control strategies from the district heating operator perspective. Based on earlier simulations on the building level, different case algorithms were simulated on a typical district heating system. The results show that even in the best case, heat production costs can be decreased by only 0.7%. However, by implementing hot water thermal storage in the system, demand response can become more profitable, resulting in 1.4% cost savings. It is concluded that the hot water storage tank can balance district heating peak loads for longer periods of time, which enhances the ability to use demand response strategies on a larger share of the building stock.

International Journal of Sustainable Energy, 2019

Effect of apartment building energy renovation on hourly power demand Optimal energy renovations ... more Effect of apartment building energy renovation on hourly power demand Optimal energy renovations of apartment buildings in Finland have a great impact on annual energy demand. However, reduction of energy demand does not necessarily translate into similar changes in peak power demand. Four different types of apartment buildings, representing the Finnish apartment building stock, were examined after optimal energy retrofits to see the influence of retrofitting on hourly power demand. Switching from district heating to ground-source heat pumps reduced emissions significantly under current energy mix. However, the use of ground-source heat pumps increased hourly peak electricity demand by 46 to 153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30 to 108% in the peak month of January. This could increase the use of high emission peak power plants and negate some of the emission benefits. Solar thermal collectors and heat recovery systems could reduce purchased heating energy to zero in summer. Solar electricity could reduce median power demand in summer, but had only a little effect on peak power demand. The reduction in peak power demand after energy retrofits was less than the reduction in energy demand.

Energy Conversion and Management, 2019

Climate change is one of the biggest challenges at the present time, and to tackle such issue, so... more Climate change is one of the biggest challenges at the present time, and to tackle such issue, solar energy and efficient buildings, in general, can be used. The goal is to design and optimize photovoltaic based decentralized district heating system and later compare it-economically and technically-against three different optimized typologies of solar district heating system in Nordic conditions. The photovoltaic based decentralized system consists of one centralized low temperature tank charged by photovoltaic and air-water heat pumps and a borehole thermal energy storage, while the decentralized high temperature tank charged by an individual water-water heat pump in each house. The centralized warm tank charges the borehole thermal energy storage. The other three systems are photovoltaic based centralized, roof-mounted solar thermal based centralized and roof-mounted solar thermal based decentralized district heating systems. In solar thermal based systems, collectors are used to directly charge the short-term storage tanks instead of the photovoltaics/heat pump combination. The proposed system is simulated using TRNSYS software. Lastly, purchased electricity and life cycle costs of the system are minimized using multi-objective optimization and the genetic algorithm. The results indicated that the decentralized photovoltaic based system outdoes all the other systems in terms of techno-economic performance. The purchased electricity can be reduced by 22% while at the same time life cycle cost can be reduced up to 40%, compared to the worst optimized system (solar thermal based centralized system). Moreover, the decentralized photovoltaic based energy system has a payback period of 9-27 years, compared to the solar thermal based system and the conventional single building-heat pump system, i.e. around 17-58 years and 15 years, respectively. The highest renewable energy fraction for heating can be close to 99% for this system. The decentralization and electrical based district systems are better in terms of life cycle cost, payback period and in terms of technical performance, compared to traditional single house and solar thermal based district heating systems.

International Journal of Sustainable Energy, 2018

Towards the EU emissions targets of 2050: Optimal energy renovation measures of Finnish apartment... more Towards the EU emissions targets of 2050: Optimal energy renovation measures of Finnish apartment buildings Member countries of the European Union have released targets to reduce carbon dioxide emissions by 80% by the year 2050. Energy use in buildings is a major source of these emissions, which is why this study focused on the cost-optimal renovation of Finnish apartment buildings. Apartment buildings from four

Solar Energy, 2018

A solar community meets a significant amount of its energy demand through solar energy. In a high... more A solar community meets a significant amount of its energy demand through solar energy. In a high latitude country like Finland, the seasonal mismatch of solar availability makes it very difficult to achieve high renewable energy fractions without seasonal storage. In this study, a solar community located in Finland was optimized with respect to energy demand and life cycle cost. To gain better understanding of both technical and economical scaling effects, the optimization was done separately for four cases with 50, 100, 200 and 500 buildings. The study was performed for Finnish conditions using dynamic TRNSYS simulations and optimized with a genetic algorithm, using the MOBO optimization tool. The modeled energy system had solar thermal collectors and solar electric panels for energy generation, two centralized short-term storage tanks and a seasonal borehole thermal energy storage system (BTES) for energy storage, and a ground source heat pump for additional heat generation. The larger communities provided noticeable cost-benefits when aiming for high performance. Larger seasonal storages allowed more direct utilization of seasonally stored heat, lowering the need for the heat pump and reducing electricity demand. Comparing the best and worst performing optimal energy system, annual demand for heating electricity was reduced by 80%. Renewable energy fractions close to 90% for heating were possible for all community sizes, but the large communities could obtain them with about 20% lower costs.

Applied Energy, 2018

Solar thermal energy is widely recognized as one of the most important renewable energy resources... more Solar thermal energy is widely recognized as one of the most important renewable energy resources. However, in high latitudes, due to various climatic and mismatch challenges, such solar district heating networks are difficult to implement. The objective of the paper is to optimize and compare two different design layouts and control strategies for solar district heating systems in Finnish conditions. The two different designs proposed are a centralized and a semidecentralized solar district heating system. The centralized system consists of two centralized short-term tanks operating at different temperature levels charged by a solar collector and heat pumps. Borehole thermal energy storage is also charged via these two centralized tanks. In contrast, the semi-decentralized system consists of one centralized low temperature tank charged by a solar collector and a borehole thermal energy storage and decentralized high temperature tank charged by an individual heat pump in each house. In this case, borehole thermal energy storage is charged only by the centralized warm tank. These systems are designed using the dynamic simulation software TRNSYS for Finnish conditions. Later on, multi-objective optimization is carried out with a genetic algorithm using the MOBO (Multiobjective building optimizer) optimization tool, where two objectives, i.e. purchased electricity and life cycle costs, are minimized. Various design variables are considered, which included both component sizes and control parameters as inputs to the optimization. The optimization results show that in terms of life cycle cost and purchased electricity, the decentralized system clearly outperforms the centralized system. With a similar energy performance, the reduction in life cycle cost is up to 35% for the decentralized system. Both systems can achieve close to 90% renewable energy fraction. These systems are also sensitive to the prices. Furthermore, the results show that the solar thermal collector area and seasonal storage volume can be reduced in a decentralized system to reduce the cost compared to a centralized system. The losses in the centralized system are 40-12% higher compared to the decentralized system. The results also show that in both systems, high performance is achieved when the borehole storage is wider with less depth, as it allows better direct utilization of seasonally stored heat. The system layout and controls varied the performance and life cycle cost; therefore it is essential to consider these when implementing such systems.

Renewable Energy, 2018

Solar energy use in Nordic countries suffers from a high seasonal mismatch of generation and dema... more Solar energy use in Nordic countries suffers from a high seasonal mismatch of generation and demand. However, given a large enough community, seasonal thermal storage could be utilized to store summertime heat gains for use in winter. This simulation study examined a Finnish case of fully electric solar heating, where heat pumps (HP) powered by photovoltaic (PV) panels were used for generating heat for both immediate use and for seasonal storage through a borehole thermal energy storage (BTES) system. Multi-objective optimization of LCC and energy use was performed by a genetic algorithm and TRNSYS simulations. Comparison was done between communities of a 100 and 500 buildings. The need for purchased electricity was between 40 and 26 kWh/m 2 per year for the optimal configurations. For the same cases the life cycle cost was between 220 and 340 V/m 2. Up to 98% renewable energy fraction was obtained for heating, showing that even in Finland it is possible to provide practically all heating by solar energy. The PV-type heating system was also compared to a solar thermal heating system from a previous study and it was found that the new design had as much as 36% lower life cycle cost.