District heating and energy efficiency in detached houses of differing size and construction

House envelope measures and conversion of heating systems can reduce primary energy use and CO₂ emission in the existing Swedish building stock. We analysed how the size and construction of electrically heated detached houses affect the potential for such measures and the potential for cogenerated district heating. Our starting point was two typical houses built in the 1970s. We altered the floor plans to obtain 6 houses, with heated floor space ranging between 100 and 306 m². One of the houses was also analysed for three energy standards with differing heat loss rates. CO₂ emission, primary energy use and heating cost were estimated after implementing house envelope measures, conversions to other heating systems and changes in the generation of district heat and electricity. The study accounted for primary energy, including energy chains from natural resources to useful heat in the houses. We showed that conversion to district heating based on biomass, together with house envelope measures, reduced the primary energy use by 88% and the CO₂ emission by 96%, while reducing the annual societal cost by 7%. The choice of end-use heating system was decisive for the primary energy use, with district heating being the most efficient. Neither house size nor energy standard did significantly change the ranking of the heating systems, either from a primary energy or an economic viewpoint, but did affect the extent of the annual cost reduction after implementing the measures.     

Perspectives on implementing energy efficiency in existing Swedish detached houses

In this study, we first analyse energy-efficiency measures in existing electrically heated houses in Sweden from a societal economic perspective. Measures to a house envelopes and to energy supply chains are evaluated through a system analysis approach and we include the external costs of climate change and the effect of different Swedish climatic zones. We find that in a typical house from the 1970s, conversion from electric heating is highly motivated since the mitigation cost of conversion is lower than the estimated external costs of emitted CO₂. Both conversions and house envelope measures are more motivated in the northern part of the country, where there is a higher heat demand. A successful implementation of changes requires them to be attractive for consumers to adopt. We therefore secondly analyse the economic conditions for Swedish house owners to implement societal economic cost-efficient measures. We include the economic influence of an investment subsidy for heating system conversion, an income tax deduction for changing windows, customer electricity tax, real estate tax and of the cost of purchased energy from different energy suppliers. Apart from the economics, several other factors affect a house owner's decision to change heating systems. We therefore thirdly analyse house owners’ perceptions of different heating supply alternatives based on the results of two comprehensive questionnaires. These different perspectives are combined in a discussion whether the studied policy instruments encourage house owners to implement changes in accordance with the energy-efficiency goals of decision makers. We find that the investment subsidy could be useful to break the lock-in effect of resistance heaters, which house owners seemed to experience. The electricity tax makes heating systems in line with national goals more competitive and efficiency measures to the house envelope more profitable. The reduction of the electricity tax in the northern part of the country has the opposite effect. Also, the increase in real estate tax when implementing energy-efficiency measures gives a contradictory message. The price differences between energy suppliers has a larger impact on the house owners’ economic conditions than both subsidies and tax rate changes, and possibly also affect the house owner's attitudes towards various systems.     

Role of energy efficiency standards in reducing CO2 emissions in Germany: An assessment with TIMES

Energy efficiency is widely viewed as an important element of energy and environmental policy. Applying the TIMES model, this paper examines the impacts of additional efficiency improvement measures (as prescribed by the ACROPOLIS project) over the baseline, at the level of individual sectors level as well as in a combined implementation, on the German energy system in terms of energy savings, technological development, emissions and costs. Implementing efficiency measures in all sectors together, CO₂ reduction is possible through substitution of conventional gas or oil boilers by condensing gas boilers especially in single family houses, shifting from petrol to diesel vehicles in private transport, increased use of electric vehicles, gas combined cycle power plants and CHP (combined heat and power production) etc. At a sectoral level, the residential sector offers double benefits of CO₂ reduction and cost savings. In the transport sector, on the other hand, CO₂ reduction is the most expensive, using bio-fuels and methanol to achieve the efficiency targets.     

地源热泵运行经济性分析

根据北方寒冷地区冬天室外温度偏低的特点,提出利用地源热泵供暖。地源热泵存在三种驱动方式：电动机、柴油机、燃气机。三种辅助供暖热源：电锅炉、燃油锅炉、燃气锅炉。本文对其一次能源利用率和燃料价格变动时,系统运行经济性进行比较分析,得出燃气热泵的供暖费用比锅炉房集中供热的费用要高6％;电动热泵的供暖费用比锅炉房集中供热费高40％;柴油机热泵的供暖费用比锅炉房集中供暖高出57％。     

Reduction of CO2 emission and oil dependency with biomass-based polygeneration

We compare different options for the use of lignocellulosic biomass to reduce CO₂ emission and oil use, focusing on polygeneration of biomass-based motor fuels and electricity, and discuss methodological issues related to such comparisons. The use of biomass can significantly reduce CO₂ emission and oil use, but there is a trade-off between the reductions in CO₂ emission and oil use. Bioelectricity from stand-alone plants replacing coal-based electricity reduced CO₂ emission by 99 kg per GJ biomass input but gave no oil use reduction. Stand-alone produced methanol replacing diesel reduced the CO₂ emission with 38 kg and the oil use with 0.67 GJ per GJ biomass, indicating that a potential CO₂ emission reduction of 90 kg is lost per GJ oil reduced. CO₂ emission and oil use reduction for alternatives co-producing fuel and electricity fall between the stand-alone alternatives. Plug-in hybrid-electric vehicles using bioelectricity reduced CO₂ emission by 75–88 kg and oil use by 0.99–1.2 GJ, per GJ biomass input. Biomass can also reduce CO₂ emission and/or oil use more efficiently if fossil-fuel-fired boilers or electric heating is replaced by district heating from biomass-based combined heat and power generation. This is also true if electricity or motor fuel is produced from black liquor gasification in pulp mills or if wood is used instead of concrete in building construction. Biomass gasification is an important technology to achieve large reductions, irrespective of whether CO₂ emission or oil use reduction is prioritised.     

The role of district heating in future renewable energy systems

Based on the case of Denmark, this paper analyses the role of district heating in future Renewable Energy Systems. At present, the share of renewable energy is coming close to 20 per cent. From such point of departure, the paper defines a scenario framework in which the Danish system is converted to 100 per cent Renewable Energy Sources (RES) in the year 2060 including reductions in space heating demands by 75 per cent. By use of a detailed energy system analysis of the complete national energy system, the consequences in relation to fuel demand, CO₂ emissions and cost are calculated for various heating options, including district heating as well as individual heat pumps and micro CHPs (Combined Heat and Power). The study includes almost 25 per cent of the Danish building stock, namely those buildings which have individual gas or oil boilers today and could be substituted by district heating or a more efficient individual heat source. In such overall perspective, the best solution will be to combine a gradual expansion of district heating with individual heat pumps in the remaining houses. Such conclusion is valid in the present systems, which are mainly based on fossil fuels, as well as in a potential future system based 100 per cent on renewable energy.     

Performance assessment of a Stirling engine plant for local micro‐cogeneration

In this paper, we evaluate the viability of a 9.5‐kW_e wooden pellet‐fueled Stirling engine‐based micro‐cogeneration plant as a substitute for small‐scale district heating. The district heating systems against which the micro‐cogeneration plant is compared are based either on a pellet‐fueled boiler or a ground‐source heat pump. The micro‐cogeneration and district heating plants are compared in terms of primary energy consumption, CO₂ emissions, and feasibility of the investment. The comparison also considers an optimally operated individual 0.7‐kW_e pellet‐fueled Stirling engine micro‐cogeneration system with exhaust gas heat recovery. The study is conducted in two different climates and contributes to the knowledge base by addressing: (i) hourly changes in the Finnish electricity generation mix; and (ii) uncertainty related to what systems are used as reference and the treatment of displaced grid electricity. Our computational results suggest that when operated at constant power, the 9.5‐kW_e Stirling engine plant results in reduced annual primary energy use compared with any of the alternative systems. The results are not sensitive to climate or the energy efficiency or number of buildings. In comparison with the pellet‐fueled district heating plant, the annual use of primary energy and CO₂ emissions are reduced by a minimum of 25 and 19%, respectively. Owing to a significant displacement of grid electricity, the system's net primary energy consumption appears negative when the total built area served by the plant is less than 1200 m². On the economic side, the maximum investment cost threshold of a CHP‐based district heating system serving 10 houses or more can typically be positive when compared with oil and pellet systems, but negative when compared with a corresponding heat pump system. Copyright © 2010 John Wiley & Sons, Ltd.     

Transitioning electricity systems: The environmental benefits and economic cost of repurposing surplus electricity in non-conventional end users

A power grid with a lower global warming impact has the potential to extend its benefits to energy systems that conventionally do not utilize electricity as their primary energy source. This study presents the case of Ontario where the role of complementing policies in transitioning electricity systems is assessed. The policy cost to incentivize surplus low emission electricity via an established mechanism for the transportation sector has been estimated (Electric and Hydrogen Vehicle Incentive Program). It is estimated that the 9056 (4760 battery and 4296 plug-in hybrid) electric vehicles that qualified for incentives from the provincial government at the end of 2016 vehicles cost $732.5-$883.9 to reduce a tonne of CO_2,e emissions over an eight year lifetime. This is then compared with the potential cost incurred by two power to gas energy hubs that utilize clean surplus electricity from the province to offset emissions within the natural gas sector. The use of hydrogen-enriched natural gas and synthetic natural gas (SNG) offsets emissions at $87.8 and $228.7 per tonne of CO_2,e in the natural gas sector. This analysis highlights the potential future costs for incentivizing new clean technologies such as electric vehicles and power to gas energy hubs in jurisdictions with a transitioning electricity system.     

Modeling of current and future energyintensity and greenhouse gas emissions ofthe Lebanese industrial sector: assessmentof mitigation options

Greenhouse gas emissions in Lebanon mainly come from energy activities, which are responsible for 85% of all CO₂ emissions. The CO₂ emissions from energy use in manufacturing industries and construction represent 24% of the total emissions of the energy sector. Lebanese manufacturers' accounted for 39.15 million gigajoules of fuel consumption for heat and power generation in 1994, including both fuel used directly and fuel burned remotely to generate electricity used in the sector. In addition to being processed by combustion, CO₂ is generated in calcining of carbonates in the manufacture of cement, iron and glass. Electricity, the most expensive form of energy, represented 25.87% of all fuel used for heat and power. Residual fuel oil and diesel, which are used mainly in direct combustion processes, represent 26.85 and 26.55% of all energy use by industry, respectively. Scenarios for future energy use and CO₂ emissions are developed for the industrial sector in Lebanon. The development of the baseline scenario relied on available data on major plants' outputs, and on reported amounts of fuels used by the industrial sector as a whole. Energy use in industry and the corresponding greenhouse gas (GHG) emissions for Lebanon are projected in baseline scenarios that reflect technologies, activities and practices that are likely to evolve from the base year 1994 to year 2040. Mitigation work targets a 15% of CO₂ emissions from the baseline scenario by year 2005 and a 20–30% reduction of CO₂ emissions by year 2040. The mitigation options selected for analysis are screened on the basis of GHG emissions and expert judgement on the viability of their wide-scale implementation and economic benefits. Using macroeconomic assessment and energy price assumptions, the final estimates of potential GHG emissions and reduction costs of various mitigation scenarios are calculated. The results show that the use of efficient electric motors, efficient boilers and furnaces with fuel switching from fuel oil to natural gas has the largest impact on GHG emissions at a levelized annual cost that ranges from −20 to −5 US$/tonne of CO₂ reduced. The negative costs are indicative of direct savings obtained in energy cost for those mitigation options.     

Emission operational strategy for combined cooling,heating, and power systems

Integrated Energy Systems (IES), as technology that use thermal activated components to recover waste heat, are energy systems that offer key solution to global warming and energy security through high overall energy efficiency and better fuel use. Combined Cooling, Heating, and Power (CCHP) Systems are IES that use recovered thermal energy from the prime mover to produce heating and cooling for the building. The CCHP operational strategy is critical and it has to be considered in a well designed system since it defines the ultimate goal for the benefits expected from the system. One of the most common operational strategies is the cost-oriented strategy, which allows the system to operate at the lowest cost. A primary energy strategy (PES) optimizes energy consumption instead of cost. However, as a result of the worldwide concern about global warming, projects that target reduction of greenhouse gas (GHG) emissions have gained a lot of interest. Therefore, for a CCHP system, an emission strategy (ES) would be an operational strategy oriented to minimize emission of pollutants. In this study, the use of an ES is proposed for CCHP systems targeted to reduce emission of pollutants. The primary energy consumption (PEC) reduction and carbon dioxide (CO₂) emission reduction obtained using the proposed ES are compared with results obtained from the use of a PES. Results show that lower emission of CO₂ is achieved with the ES when compared with the PES, which prove the advantage of the ES for the design of CCHP systems targeted to emissions reduction.     

Market diffusion,technological learning,and cost-benefit dynamics of condensing gas boilers in the Netherlands

High costs often prevent the market diffusion of novel and efficient energy technologies. Monitoring cost and price decline for these technologies is thus important in order to establish effective energy policy. Here, we present experience curves and cost-benefit analyses for condensing gas boilers produced and sold in the Netherlands between 1981 and 2006. For the most dominant boiler type on the Dutch market, i.e., condensing gas combi boilers, we identify learning rates of 14±1% for the average price and 16±8% for the additional price relative to non-condensing devices. Economies of scale, competitive sourcing of boiler components, and improvements in boiler assembly are among the main drivers behind the observed price decline. The net present value of condensing gas combi boilers shows an overall increasing trend. Purchasing in 2006 a gas boiler of this type instead of a non-condensing device generates a net present value of 970 EUR (Euro) and realizes CO₂ (carbon dioxide) emission savings at negative costs of −120 EUR per tonne CO₂. We attribute two-thirds of the improvements in the cost-benefit performance of condensing gas combi boilers to technological learning and one-third to a combination of external effects and governmental policies.     

Adoption of innovative heating systems—needs and attitudes of Swedish homeowners

Questionnaire surveys of Swedish homeowners of detached houses were carried out in 2004 and 2007 to understand their needs and attitudes towards attributes of innovative heating systems (IHSs) comprised of a bedrock heat pump, district heating, or a wood pellet boiler. In each occasion 1,500 homeowners were randomly selected. The response rate was 42% in 2004 and 48% in 2007. Results showed that the majority of the respondents were satisfied with their existing heating system and did not intend to install new systems. Economic factors and functional reliability were the most important factors in the respondents’ choices of heating system, while environmental factors were of lower importance. Among the IHSs, respondents had the most favorable attitude towards bedrock heat pumps followed by district heating and pellet boilers. But the attitude was more favorable towards electric boilers than for pellet boilers. The least favorable attitude was towards oil boilers. Between 2004 and 2007, there was a positive change in respondents’ attitude towards IHSs and electric boilers, and a negative change in attitude towards resistance heaters and oil boilers.     

A comparison of the energy and carbon implications of new systems of energy provision in new build housing in the UK

The built environment needs to develop sustainable, decarbonised, low energy systems and approaches that are socially acceptable and economically beneficial. The UK mainstream house construction industry is being driven, through policy and regulation, towards achieving this end without evidence of how these new systems of provision are used by passively adopting households. In this paper energy use, consequential emissions of CO₂, and annual running costs for a case study comprising 14 newly constructed low energy affordable homes are evaluated. Four different energy typologies are compared: ground sourced heat pumps; active solar (thermal and photovoltaic); passive solar and mechanical ventilation with heat recovery; conventional high efficiency gas boiler. The carbon embodied in construction and emitted over a 20 year occupation period for each typology is calculated. Ground source heat pumps have the highest annual primary energy demand, CO₂ emission and annual running costs over the 20 year period. The homes with active solar technologies provided most benefit across all three evaluation criteria. Energy and CO₂ emissions associated with end uses other than heating were similar to the UK average. This poses significant questions on the probability of policy application in the real world to deliver projected reductions in emissions of CO₂.     

Analysis of ground source heat pumps with horizontal ground heat exchangers for northern Japan

Computer simulation and analysis of a ground source heat pump system with horizontal ground heat exchangers operating in heating (max 5.5 kW) and cooling (max 3.3 kW) mode was carried out for a typical residential house, with 200 m² of living space, located in Sapporo (Japan). In spite of high electricity rate, the ground source heat pump system is more beneficial alternative for space heating than an oil furnace and an electric resistance system. Besides, the heat pump technology offers relatively low thermal degradation of the ground environment, lower cost of heating and cooling, higher operating efficiency than electric resistance heating or air-source heat pump and is environmentally clean, i.e. without greenhouse gas emission, if the electricity is generated from renewable energy resources, such as wind and solar. The use of the cooling mode can provide further benefits like a shorter investment payback and human thermal comfort in summer. As a result, application of horizontal loops for new and retrofit residential and commercial use in northern Japan is feasible particularly in farmland areas.     

Coal-based synthetic natural gas (SNG): A solution to China’s energy security and CO2 reduction?

Considering natural gas (NG) to be the most promising low-carbon option for the energy industry, large state owned companies in China have established numerous coal-based synthetic natural gas (SNG) projects. The objective of this paper is to use a system approach to evaluate coal-derived SNG in terms of life-cycle energy efficiency and CO₂ emissions. This project examined main applications of the SNG and developed a model that can be used for evaluating energy efficiency and CO₂ emissions of various fuel pathway systems. The model development started with the GREET model, and added the SNG module and an end-use equipment module. The database was constructed with Chinese data. The analyses show when the SNG are used for cooking, power generation, steam production for heating and industry, life-cycle energies are 20–108% higher than all competitive pathways, with a similar rate of increase in life-cycle CO₂ emissions. When a compressed natural gas (CNG) car uses the SNG, life-cycle CO₂ emission will increase by 150–190% compared to the baseline gasoline car and by 140–210% compared to an electric car powered by electricity from coal-fired power plants. The life-cycle CO₂ emission of SNG-powered city bus will be 220–270% higher than that of traditional diesel city bus. The gap between SNG-powered buses and new hybrid diesel buses will be even larger—life-cycle CO₂ emission of the former being around 4 times of that of the latter. It is concluded that the SNG will not accomplish the tasks of both energy conservation and CO₂ reduction.     

Energy and environmental implications of carbon emission reduction targets: Case of Kathmandu Valley,Nepal

This paper analyzes the sectoral energy consumption pattern and emissions of CO₂ and local air pollutants in the Kathmandu Valley, Nepal. It also discusses the evolution of energy service demands, structure of energy supply system and emissions from various sectors under the base case scenario during 2005–2050. A long term energy system planning model of the Kathmandu Valley based on the MARKet ALlocation (MARKAL) framework is used for the analyses. Furthermore, the paper analyzes the least cost options to achieve CO₂ emission reduction targets of 10%, 20% and 30% below the cumulative emission level in the base case and also discusses their implications for total cost, technology-mix, energy-mix and local pollutant emissions. The paper shows that a major switch in energy use pattern from oil and gas to electricity would be needed in the Valley to achieve the cumulative CO₂ emission reduction target of 30% (ER30). Further, the share of electricity in the cumulative energy consumption of the transport sector would increase from 12% in the base case to 24% in the ER30 case.     

The benefits of the transition from fossil fuel to solar energy in Libya: A street lighting system case study

The Libyan economy is dominated by the oil and the gas industry which are considered as the primary energy sources for the generating power plants. With the increased energy demands in the near future, Libya will be forced to burn more oil and gas. This, in turn will result in reducing the country revenue, threatening the economy and increasing the CO₂ emission. This triggers the alarm for Libya to an urgent plan to diversify the energy sources through using sustainable energy. The sun showers Libya every day by a huge amount of sunshine, especially during the peaks in the summer days. Recently, the country has been struggling to satisfy its escalating energy demands. The residential and street lighting loads constitute more than 50% of the electricity demands in Libya. Street lighting consumes more than 3.996 TW h, which is around one fifth of the energy demands in Libya. Energy conservation and transition from fossil fuel to renewable energy could have significant profit on the energy sector in Libya. For example, Libya is still relying on the old-fashioned, inefficient and unsustainable street lighting systems. Replacing the old technology lighting systems with up-to-date solar powered lighting system can achieve energy saving and sustainability. In this paper, improving the energy situation in Libya through replacing the high pressure sodium street lighting systems with solar powered LED street lighting systems is investigated. A four km road is chosen as a case study. Four alternatives are analyzed; grid-powered high pressure sodium lamp street lighting system, grid-powered LED lamp street lighting system, stand-alone solar powered LED street lighting system and grid-connected solar powered LED street lighting system. The four options are compared in terms of the capital cost, maintenance cost, total cost, fuel cost and the CO₂ emission. Replacing the high pressure sodium lamp system with LED lamp system saves 75% of energy and reduces the CO₂ emission by 75%. The stand-alone solar powered LED lighting system cuts the CO₂ emission, saves the fuel and is economically feasible. Furthermore, improvement is attained if the solar powered lighting system is connected to the grid where the excess energy is fed to the grid. The two solar powered options are economically feasible and sustainable.     

Five-year technology selection optimization to achieve specific CO2 emission reduction targets

Long-term planning for replacement of fossil fuel energy technologies with renewables is of great importance for achieving GHG emission reduction targets. The current study is focused on developing a five-year mathematical model for finding the optimal sizing of renewable energy technologies for achieving certain CO₂ emission reduction targets. A manufacturing industrial facility which uses CHP for electricity generation and natural gas for heating is considered as the base case in this work. Different renewable energy technologies are developed each year to achieve a 4.53% annual CO₂ emission reduction target. The results of this study show that wind power is the most cost-effective technology for reducing emissions in the first and second year with a cost of 44 and 69 CAD per tonne of CO₂, respectively. Hydrogen, on the other hand, is more cost-effective than wind power in reducing CO₂ emissions from the third year on. The cost of CO₂ emission reduction with hydrogen doesn't change drastically from the first year to the fifth year (107 and 130 CAD per tonne of CO₂). Solar power is a more expensive technology than wind power for reducing CO₂ emissions in all years due to lower capacity factor (in Ontario), more intermittency (requiring mores storage capacity), and higher investment cost. A hybrid wind/battery/hydrogen energy system has the lowest emission reduction cost over five years. The emission reduction cost of such hybrid system increases from 44 CAD per tonne of CO₂ in the first year to 156 CAD per tonne of CO₂ in the fifth year. The developed model can be used for long-term planning of energy systems for achieving GHG emission targets in a regions/country which has fossil fuel-based electricity and heat generation infrastructure.     

供热一次网阻力分析

我国北方地区冬季采暖集中供热发展迅速,热水锅炉供热应用普遍。本文着重分析一次网供热系统阻力的大小,这关系到主干网循环泵选择,关系到一次网循环泵运行成本、能耗的高低。一次网循环泵扬程选择往往高于供热系统的实际阻力,使循环泵运行时远远偏离最佳工作点,严重浪费电能。     

Energy conservation on Nova Scotia farms: Baseline energy data

Direct energy use is a small but essential component of the farm greenhouse gas (GHG) budget. Improvements in energy efficiency and renewable energy can help reduce farm operating costs, improve air quality and reduce GHG emission levels. Energy conservation is especially important in Nova Scotia (NS), Canada, where fossil fuels, particularly coal, remain the primary source of electrical generation. Responses from mail surveys were used to establish baseline data on a cross-section of NS farms with respect to direct energy costs and usage to demonstrate differences in farm type and size. A 32% (N=224) response rate was achieved. Based on this survey, the average energy bill for a NS farm in 2004 was $11,228, with most (61.7%) of their energy cost attributable to the purchase of petroleum products. Almost all farmers (96.4%) indicated that their energy cost was a primary concern. Farmers identified the operation of vehicles and mobile equipment, as well as lighting and heating as having the greatest energy requirements in their operations. Energy usage varied with farm type and size. NS farms consumed 1.2 petajoules of energy equivalent to 127 kilotonnes of CO₂ with 52.7% of emissions from electricity use in 2004.