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 different construction years (pre-1976, 1976-2002, 2003-2009 and post-2010) were modelled, using three different heating systems: district heating, ground-source heat pump and exhaust air heat pump. Multi-objective optimisation was utilised to find the most cost-effective energy renovation measures. Most cost-effective renovation measures were ground-source heat pumps, demand-based ventilation and solar electricity. Additional thermal insulation of walls was usually too expensive. By performing only the cost-effective renovations, the emissions could be reduced by 80%, 82%, 69% and 68%, from the oldest to the newest buildings, respectively. This could be done with the initial investment cost of 296, 235, 115 and 104 €/m
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, respectively.
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 houses and investment levels. With all the other heating systems, emission reductions of 20% to 75% were possible. The most cost-effective individual renovation measures were the installation of air-to-air heat pumps for auxiliary heating and improving the thermal insulation of external walls.
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 such plans. Annual energy storage efficiencies from 48% to 69% were obtained for the BTES. Waste heat could generate 37–89% of the annual heat demand. Cost estimations of waste heat storage using BTES are not available in the literature. As an important finding in this study, a levelized cost of heat of 10.5–23.5 €/MWh was obtained for various BTES configurations used for incineration waste heat storage. In the three most effective cases, the stored heat reduced annual CO2 emissions of the residential area by 42%, 64% and 86%. Thus, the solution shows great potential for reducing carbon emissions of district heating in grids connected to waste incineration plants.
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 power demand of electricity in district heated and wood heated buildings by as much as 100%. On the other hand, peak power demand in buildings with direct electric heating was reduced by 30 to 40%. On the building stock level, the demand reduction in buildings with direct electric heating could compensate for the increase in the share of buildings with ground-source heat pumps, so that the national peak electricity demand would not increase. This prevents the increase of demand for high emission peaking power plants as heat pump penetration rises. However, a use is needed for the excess solar electricity generated by the optimally retrofitted buildings, because much of the solar electricity cannot be utilized in the single-family houses during summer.
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.
•Optimized energy retrofits reduced energy consumption of building archetypes.•Four retrofitting scenarios for Finnish building stock by 2050 were analyzed.•District heating demand was reduced by ...25–63 % compared to business-as-usual by 2050.•Electricity demand did not rise despite increased heat pump deployment.•CO2 emissions in the retrofit scenarios were reduced by 50–75 % by 2050.
Finland and the European Union aim to reduce CO2 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. CO2 emissions in the different scenarios were reduced by 50–75 % by 2050 using current emissions factors.
The Finnish Government target of carbon neutrality by 2035 is challenging for the district heat (DH) systems of Finnish cities, as nearly 50% of the DH fuels are still fossil or peat. The DH price in ...Finnish cities is rising intensively. To avoid energy poverty, it is imperative to develop low-carbon DH solutions affordable for all customers. The feasibility of various low-carbon scenarios supplying a DH network is investigated with three different energy renovation levels. Biomass combustion technologies (combined heat and power (CHP) and heat only boiler (HOB)) and waste heat recovery technologies (Heat Pump and Electric Boiler) are analyzed. The economic and sensitivity analyses of the DH network are carried out from utility and end-user viewpoints. The operation cost and break-even price of heat are calculated in different renovation levels. Biomass HOB has the lowest operation cost at all renovation levels followed by waste heat-heat pump. Waste heat-heat pump + electric boiler has the lowest total cost, 53–58 €/MWh, at all renovation levels. Waste heat recovery scenarios were found sensitive to changes in electricity price. Waste heat-heat pump has the lowest overall emissions, whereas biomass combustion causes high emissions of biogenic CO2, NOx and particulate matter.
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•Biomass combustion scenarios have lower operation cost but higher investment.•A novel scenario composed of waste heat-heat pump and electric boiler is proposed. .•Combination of heat pump and electric boiler has lowest total cost, 53–58 €/MWh.•Life-time costs of energy renovations are higher than the savings in heating costs.•Waste heat recovery scenarios are sensitive to changes in electricity price.
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 system was replaced with Case 3 and the emissions reduction cost was 3.74 €/kg.CO2/yr. The relative emissions reduction was 91% when the buildings were deep renovated and integrated with Case 3 when compared to the reference system with non-renovated buildings and the emission reduction cost was 11.9 €/kg.CO2/yr. Such district heating systems could help in meeting Europe’s emissions target for 2050.
•Sharing of surplus heat and electricity produced by CHP plants in different types of buildings.•Individually prioritized control of CHP plants with direct local sharing and minimal storage ...capacity.•Energy sharing reduced primary energy consumption by 1–9% with biogas.•Excess energy minimized by thermal tracking.
All over the world, including Japan, there are targets to decrease building energy consumption and increase renewable energy utilization. Combined heat and power (CHP) plants increase energy efficiency and are becoming popular in Japan. CHP plants produce both heat and power simultaneously, but there is not always a need for both. A cluster of several different buildings can increase total efficiency and reduce primary energy (PE) consumption by sharing excess heat and electricity between neighboring buildings. If the generated energy comes from renewable sources, energy sharing makes it easier to reach the net zero energy balance. By adjusting CHP sizes and operation patterns, the wasted heat and primary energy consumption can be minimized.
Energy sharing has been explored in situations with identical buildings and centrally administered energy systems before, but not with different building types with separate systems. In this study, a cluster of Japanese office and residential buildings were combined to allow heat and electricity sharing based on cogeneration, using individually prioritized control (IPC) systems. TRNSYS simulation was used to match energy generation with pregenerated demand profiles. Absorption cooling was utilized to increase the benefits of local heat generation. Different CHP operation modes and plant sizes were tested.
The benefit of surplus energy sharing depends on the CHP capacities and the fuel type. When using biogas, larger CHP plants provided lower total primary energy consumption, in the most extreme case lowering it by 71%, compared to the conventional case. Using natural gas provided only a 6% decrease. The savings resulting from energy sharing were between 1% and 9% with biogas and between 1% and 6% using natural gas. The least amount of PE was consumed by having large CHP plants with biogas, due to the value of renewable electricity. Using natural gas, thermal tracking had the lowest PE consumption.
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 46-153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30-108% 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.
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