Primary Energy Use Research Articles

Defining water-related energy for global comparison, clearer communication, and sharper policy

The need for energy in water provision and use is obvious, however the drivers are often complex, difficult to assess, and often inconsistently presented. Here we build a clearer definition and conceptual framework of “water-related energy”. We apply this framework to harmonise data and results across disparate studies so that regional estimates of water-related energy can be compared in a consistent way for the first time. We show how widely different boundaries have been used for analysis including or excluding: water and wastewater utilities, as well as residential, commercial, industrial, and agricultural water users. Consequently, understanding of what constitutes “water-related energy” is widely divergent. We demonstrate how up to 12.6% of total national primary energy use can be influenced by water, when (i) water-related energy of water users, and (ii) energy use by water utilities, are all included. Water heating for residential, commercial, and industrial purposes is the dominant fraction. Water and wastewater utilities use 0.4–2.3% of primary energy or 0.6–6.2% of regional electricity, mostly for water pumping. This is substantial, but lower than frequent claims in the media and reports. To answer how is miscommunication influencing policy? we undertake a novel systematic tracking of communication to demonstrate distortion between research and its application in government reports, media and policy. We show that significant confusion is caused by (i) unclear or inconsistent boundaries (ii) widely differing use of terms for water “system”, “sector”, and “supply”, (iii) frequent failure to distinguish ‘energy’ from ‘electricity’ and (iv) wide use of non-standard units. While acknowledging that media is often less accurate than government reports, and that peer-reviewed articles generally have highest overall quality, we observe miscommunication and inconsistency in all publication forms. We argue a global protocol is needed to improve consistency of analysis and sharpen policy towards sustainable water end use because this is where most water-related energy occurs. We establish a foundational framework and definitions for this protocol while recognising much more needs to be done. The strong practical and theoretical implications of the work for sustainable cleaner production are elucidated. This is timely, as global quantification of water-related energy has yet to occur particularly for water end-use which is the dominant component.

Primary energy and exergy of desalination technologies in a power-water cogeneration scheme

The primary energy consumption of a spectrum of desalination systems is assessed using operating information and technical bids for real plants configured with coproduction of electricity. The energy efficiency of desalination plants is often rated on a stand-alone basis using metrics such as specific energy consumption, gained output ratio, and second law efficiency, which can lead to inconsistent conclusions because the heat and electrical work inputs to the plant have very different exergies and costs, which must be taken into account. When both the heat and work inputs are drawn from a common primary energy source, such as the fuel provided to electricity-water coproduction systems, these inputs can be compared and combined if they are traced back to primary energy use. In the present study, we compare 48 different configurations of electricity production and desalination on the basis of primary energy use, including cases with pretreatment and hybridized systems, using performance figures from real and quoted desalination systems operating in the GCC region. The results show that, while reverse osmosis is still the most energy efficient desalination technology, the gap between work and thermally driven desalination technologies is reduced when considered on the basis of primary energy. The results also show that pretreatment with nanofiltration or hybridization of multiple desalination systems can help to reduce energy requirements. Additionally, the specific type of power plant in the coproduction scheme and its operating parameters can have a significant impact on the performance of desalination technologies relative to one other.

Annual performance experiments of an earth-air heat exchanger fresh air-handling unit in severe cold regions: Operation, economic and greenhouse gas emission analyses

This paper proposes a fresh air-handling unit, comprising an earth-air heat exchanger (EAHE) and a heat recovery unit, to solve the problem of insufficient fresh air and save primary energy use in severe cold regions. A new construction of double-layer buried pipes was adopted to enhance heat transfer and save land use. Annual performance of system from January to December 2017 was evaluated by analyzing inlet/outlet air parameters, thermal capacity, and power consumption variation. Different operation modes were adopted to simulate use patterns of various building styles. Results show that during heating operation, the maximum temperature produced by EAHE was 22.2 °C and its maximum heating capacity was 7718 W. The average temperature drop during the cooling operation was 13.6 °C. The system can provide fresh air with sufficient temperature independently. Both heat and mass transfer exist inside the buried pipes when operated under the cooling mode. Latent cooling capacity occupied 32.1% of total cooling capacity averagely, which reveals the importance of mass transfer. From the correlation analysis, it is clear that the heating capacity and sensible cooling capacity have the strongest correlation with inlet air temperature and the latent cooling capacity reacts to the moisture content. The average annual COP¯ of the system is 8.5. Compared to an air-source heat pump handling unit, the dynamic payback period is only 2.38 years and proposed system can further provide an 82.5% reduction in greenhouse gas emissions.

Performance assessment of a 15 kW Micro-CHCP plant through the 0D/1D thermo-fluid dynamic characterization of a double water circuit waste heat recovery system

The exploitation of renewable energy sources and the use of primary energy saving techniques have been recognized as key solutions to face climate changes. The consequent energy policies are pushing the transition from a centralized power generation system to a distributed polygeneration system able to meet simultaneous heating, cooling and electricity demand. However, small scale polygeneration plants do not ensure any primary energy and cost saving without a proper sizing and operation of the plant. Furthermore, a flexible configuration of the waste heat recovery system (WHRS) adopted for polygeneration purposes can be equally important. Therefore, starting from the experimental data concerning a 15 kW micro-CHP plant previously designed and prototyped, the paper addresses the performance assessment of a CHCP plant configuration based on the same basic engine-electric generator system through the 1D thermo-fluid dynamic characterization of an alternative double water circuit WHRS. This configuration, delivering thermal power at different temperature level, could be useful to meet thermal and cooling demand from different user or when seasonal energy demand occurs. This paper also provides an effective approach for the design of WHRS which are capable to ensure a reasonable matching between the temperature level required by the user and that provided by the plant. In this way, being the energy saving dependent on the thermal power recovered and actually exploited, and so on the temperature level which characterizes the user's heat demand, primary energy savings are more easily achievable even when small scale polygeneration applications are considered. Results shows the possibility of supplying an absorption chiller and obtaining a coolling capacity of about 10.5 kW from the resulting CHCP plant configuration.

Analyzing the Performance and Control of a Hydronic Pavement System in a District Heating Network

A hydronic pavement system (HPS) is an alternative method to clear snow and ice, which avoids the use of salt, sand, and fossil fuel in conventional snow clearance, and minimizes the risk of accidents. The aim is to analyze the performance of different control strategies for a 35,000 m2 HPS utilizing heat from a district heating and cooling (DHC) system. The key performance indicators are (1) energy performance of the HPS, and (2) primary energy use, (3) electricity production and (4) greenhouse gas (GHG) emissions from the DHC system. The methodology uses a simulation model of the HPS and an optimization model of the DHC system. Three operational strategies are analyzed: A reference scenario based on the current control strategy, and scenarios where the HPS is shut down at temperatures below −10 °C and −5 °C. The study shows that the DHC return temperature is suitable for use. By operational strategies, use during peak demand in the DHC system can be avoided, resulting in reduced use of fossil fuel. Moreover, the energy use of the HPS could be reduced by 10% and the local GHG emissions by 25%. The study emphasizes that the HPS may have positive effects on global GHG emissions, as it enables electricity production from renewable resources.

Worldwide energy use across global supply chains: Decoupled from economic growth?

Decoupling indicators are widely used to understand links between economic growth and energy use. However, traditional decoupling analyses mostly focus on domestic energy consumption (i.e., the production-based principle) and neglect off-site energy use across global supply chains to satisfy an economy’s final consumption (i.e., the consumption-based principle). Moreover, analyses for total primary energy conceal an economy’s preference for different energy sources. Therefore, this paper evaluates decoupling states of GDP from all types of primary energy use under consumption-based principle, for world economy and eight typical economies during 2000–2011. Regarding total primary energy, world economy witnessed weak decoupling in most years, and most economies studied (e.g., USA, Japan and China) achieved decoupling initially but performed negative decoupling finally. For EU, USA, Japan, Russia and India, production-based decoupling performances were generally better than consumption-based ones. Decoupling phenomena detected under production-based principle even became coupling or negative decoupling under consumption-based principle in some cases. As for each energy source, world economy decoupled from oil use, but still coupled with coal use, and gradually showed a trend to couple with natural gas and renewables use. Different energy sources showed distinct decoupling degrees from GDP, affected by individual embodied energy requirement structure. This paper uncovers potential energy decoupling delusions to deepen the understanding of relationships between energy use and economic growth.

Ecosystem maintenance energy and the need for a green EROI

A number of official energy forecasts—including those compatible with the aspirational 1.5 °C Paris Accord global temperature rise limit—see both global primary and net energy use continuing to rise, even out to 2100. Various technologies, including greatly increased use of renewable and nuclear energy, negative emission technologies such as direct air capture, and geoengineering are proposed as approaches for meeting the 1.5 °C target. In contrast, we argue that meeting this target and avoiding significant increases in extreme weather events will require marked reductions in future energy demand. We argue that the combined fossil fuel and renewable net green energy production will fall in the coming decades, after subtraction of various energy costs essential for ecosystems maintenance, including those needed to stabilise climate. At best, nuclear energy will only fractionally increase its global energy share, because of its high capital costs and political opposition arising from accident risks, waste disposal and proliferation concerns. Geoengineering will not solve fossil fuel depletion, and has serious known—and perhaps unknown—risks. We conclude that global net energy produced in an ecologically sustainable manner will start falling in a decade or so, and suggest the need to account for this at a policy level by introduction of a green EROI—EROIg.

Lifecycle Impacts of Structural Frame Materials for Multi-storey Building Systems

In this study the lifecycle primary energy and greenhouse gas (GHG) implications of multi-storeybuilding versions with different structural frame materials as well as construction systems are analysedconsidering flows from the production, operation and end-of-life phases and the full natural resourceschains. The analysed building versions include conventional and modern construction systems withlight-frame timber, reinforced concrete-frame, massive timber frame, beam-and-column timber frameor modular timber frame structural systems and are designed to the energy efficiency level of thepassive house criteria. The results show that the lifecycle primary energy use and GHG emissions forthe reinforced concrete building system are higher than those for the timber-based building systems,due primarily to the lower production primary energy use and GHG emissions as well as greater amountof biomass residues when using wood-based materials. The operation primary energy use and GHGemission for the buildings are lower when heated with cogenerated district heating compared to whenheated with electric-based heat pump, showing the significance of heat supply choice. The findingsemphasize the importance of structural frame material choice and system-wide lifecycle perspective inreducing primary energy use and GHG emissions in the built environment.

The Impact on System Performance When Renovating a Multifamily Building Stock in a District Heated Region

In Sweden, 90% of multifamily buildings utilize district heat and a large portion is in need of renovation. The aim is to analyze the impact of renovating a multifamily building stock in a district heating and cooling system, in terms of primary energy savings, peak power demands, electricity demand and production, and greenhouse gas emissions on local and global levels. The study analyzes scenarios regarding measures on the building envelope, ventilation, and substitution from district heat to ground source heat pump. The results indicate improved energy performance for all scenarios, ranging from 11% to 56%. Moreover, the scenarios present a reduction of fossil fuel use and reduced peak power demand in the district heating and cooling system ranging from 1 MW to 13 MW, corresponding to 4–48 W/m2 heated building area. However, the study concludes that scenarios including a ground source heat pump generate significantly higher global greenhouse gas emissions relative to scenarios including district heating. Furthermore, in a future fossil-free district heating and cooling system, a reduction in primary energy use will lead to a local reduction of emissions along with a positive effect on global greenhouse gas emissions, outperforming measures with a ground source heat pump.

Considering infrastructure when calculating emissions for freight transportation

In this paper, the contributions to emissions to air related to traffic infrastructure and terminals are analysed for freight transport with different modes. Data on emissions per km road or railway from existing LCA reports are adapted to a selection of road types and one type of railway line. The presented data are for air pollutants, use of primary energy and emissions of green-house gases divided into construction, maintenance and operation phases. These data are then allocated to the traffic-work produced on the infrastructure during its life span. Different allocation methods are suggested for the separate LCA-phases. The research has a focus on freight transport, why data are presented as emissions per vehicle-km for a number of truck and train types. For ports and airports, data are available per tonne of goods over quay or in- and outgoing. These results are then used to calculate the emissions added for infrastructure for freight transport chains. Examples are given showing the magnitude of emissions originating from infrastructure that can be added to tailpipe and other upstream emissions, e.g. fuel and vehicle production. In relation to tailpipe emissions the CO2 emissions from infrastructure is typically 1–7% for road and around 17% for rail. For air and sea the results will vary significantly; for typical intra-Europe routes we find a contribution from infrastructure of about 3% for air and 21–34% for sea, in relation to emissions from the vessels.

Haze Influencing Factors: A Data Envelopment Analysis Approach.

This paper investigates the meteorological factors and human activities that influence PM2.5 pollution by employing the data envelopment analysis (DEA) approach to a chance constrained stochastic optimization problem. This approach has the two advantages of admitting random input and output, and allowing the evaluation unit to exceed the front edge under the given probability constraint. Furthermore, by utilizing the meteorological observation data incorporated with the economic and social data for Jiangsu Province, the chance constrained stochastic DEA model was solved to explore the relationship between the meteorological elements and human activities and PM2.5 pollution. The results are summarized by the following: (1) Among all five primary indexes, social progress, energy use and transportation are the most significant for PM2.5 pollution. (2) Among our selected 14 secondary indexes, coal consumption, population density and civil car ownership account for a major portion of PM2.5 pollution. (3) Human activities are the main factor producing PM2.5 pollution. While some meteorological elements generate PM2.5 pollution, some act as influencing factors on the migration of PM2.5 pollution. These findings can provide a reference for the government to formulate appropriate policies to reduce PM2.5 emissions and for the communities to develop effective strategies to eliminate PM2.5 pollution.

Final and primary energy use for heating new residential area with varied exploitation levels, building energy performance and district heat temperatures

Abstract There is great potential to build new energy-efficient building blocks in combination with efficient energy supply systems. Such a development will contribute to achieve national energy and climate goals as well as the overall aim for a sustainable development. Here, we analyze final and primary energy use for heating a new residential area by using district-heating. The area, located in Vaxjo, in south Sweden has potentially varied land exploitation levels, energy performance of buildings and district heat supply/return temperatures. The results show that the district heating demand will be reduced by about 52-56% if buildings in the area meet the Swedish passive house criteria instead of the Swedish building code. The exploitation levels of construction in the area strongly influence the total heating demands. A dense instead of a low exploitation will increase the area’s heating demand more than four times. But, the heat demand density of the residential area has quite a small impact on the total heat losses of the distribution network in contrast to changed supply and return temperatures. The distribution heat losses could be reduced by up to 50% with lower supply/return temperatures. However, a reduction of district heat supply/return temperatures to 50/20oC increases electricity use for boosting hot water temperature to avoid the risk of legionella bacteria. This causes a shift from district heat production to electricity production and increases the primary energy use. The results of this study can be used for further considerations of costs and benefits of energy supply options for new residential areas.

Costs and primary energy use of heating new residential areas with district heat or electric heat pumps

The choice of a heat supply option in new residential areas depends on various factors including available local energy resources and the scale and density of the heat demand in the areas. Here, we study costs and primary energy use of using district heat (DH) and ground-source electric heat pump (EHP) for heating a residential area being developed. We consider different architecture layouts and exploitations of the area along with different building energy efficiency standards which give different heat demand densities and profiles for this residential area. The analysis shows that for existing fuel-based energy supply systems, using DH is more primary energy efficient than using EHP to supply heat to the new residential area. However, if the future production of marginal electricity is based on state-of-the art technologies utilizing renewable energy resources, using EHP can be more primary energy efficient than using DH. The initial investment costs are much lower for options using DH than for options using ground-source EHP for the different exploitation alternatives. Also, the marginal heat cost for suppling DH to the residential area, excluding the sunk capital costs, is significantly lower than the heat cost for supplying heat with ground-source EHPs. The potential use of local ground-source heat linked to the exploitation level of residential area and energy performance of the buildings should be further analyzed in comparison to the use of other types of heat sources such as ambient air or ventilation air.

General Equilibrium Analysis of the Cobenefits and Trade-Offs of Carbon Mitigation on Local Industrial Water Use and Pollutants Discharge in China.

Carbon mitigation strategies have been developed without sufficient consideration of their impacts on the water system. Here, our study evaluates whether carbon mitigation strategies would decrease or increase local industrial water use and water-related pollutants discharge by using a computable general equilibrium (CGE) model coupled with a water withdrawals and pollutants discharge module in Shenzhen, the fourth largest city in China. To fulfill China's Nationally Determined Contributions (NDC) targets, Shenzhen's GDP and welfare losses are projected to be 1.6% and 5.6% in 2030, respectively. The carbon abatement cost will increase from 56 USD/t CO2 in 2020 to 274 USD/t CO2 in 2030. The results reveal that carbon mitigation accelerates local industrial structure upgrading by restricting carbon-, energy-, and water-intensive industries, e.g., natural gas mining, nonmetal, agriculture, food production, and textile sectors. Accordingly, carbon mitigation improves energy use efficiency and decreases 55% of primary energy use in 2030. Meanwhile, it reduces 4% of total industrial water use and 2.2-2.4% of two major pollutants discharge, i.e., CODCr and NH3-N. Carbon mitigation can also decrease petroleum (2.2%) and V-ArOH (0.8%) discharge but has negative impacts on most heavy metal(loid)s pollutants discharge (increased by -0.01% to 4.6%). These negative impacts are evaluated to be negligible on the environment. This study highlights the importance of considering the energy-water nexus for better-coordinated energy and water resources management at local and national levels.

Effect of different frame materials on the primary energy use of a multi storey residential building in a life cycle perspective

Primary energy implications over the life cycle of a multi storey residential building with different building systems are explored here. The main structural materials of the buildings include precast concrete, cross laminated timber (CLT) and prefabricated timber modules (modular). The analysis covers energy and material flows from different life cycle phases of the building versions, designed to meet the energy performance of the Swedish building code (BBR) and passive house criteria. The CLT and modular buildings were found to result in lower production primary energy use and higher biomass residues compared to the concrete alternative. The heating value of the recoverable biomass residues from the production phase of the CLT building is significantly larger than the primary energy required for its production. Primary energy use for production and construction constitutes 20–30% and 36–47% of the total primary energy use for production, construction, space heating, ventilation and demolition for the BBR and passive buildings, respectively. Space heating with combined heat and power (CHP) and ventilation electricity for the BBR and passive building versions form 70–79% and 52–63%, respectively, of the total primary energy use for production, construction, space heating, ventilation and demolition for a lifespan of 80 years. The CLT and modular buildings give 20–37% and 9–17% lower total life cycle primary energy use, respectively, than the concrete alternative when space heating is from CHP.

Study of optimal sizing for residential sorption heat pump system

Gas-driven sorption heat pumps (GDSHP) show significant potential to reduce primary energy use, associated emissions and energy costs for space heating and domestic hot water production in residential applications. This study considered a bivalent heating system consisting of a sorption heat pump and a condensing boiler, and focuses on the optimal heating capacity of each of these components relative to each other. Two bivalent systems were considered: one based on a solid chemisorption cycle (GDSHPA), and one based on a resorption cycle (GDSHPB). Simulations of year-round space heating loads for two single-family houses, one in New York and the other Minnesota, were carried out and the seasonal gas coefficient of performance (SGCOP) calculated. The sorption heat pump’s design heating capacity as a fraction of the bivalent system’s total heating capacity was varied from 0 to 100%. Results show that SGCOP was effectively constant for sorption heat pump design capacity greater than 41% of the peak bivalent GDSHPA design capacity in Minnesota, and 32% for GDSHPB. In New York, these values were 42% and 34% for GDSHPA and GDSHPB respectively. The payback period was also evaluated based on postulated sorption heat pump component costs. The fastest payback was achieved with sorption heat pump design capacity between 22 and 44%.

Impact analysis of energy efficiency measures in the electrolysis process in primary aluminium production

The Paris Agreement includes the goals of ‘holding the increase in the global average temperature to well below 2°C above pre-industrial levels’ and ‘making finance flows consistent with a pathway towards low greenhouse gas emissions’. Industrial energy efficiency will play an important role in meeting those goals as well as becoming a competitive advantage due to reduced costs for companies. The aluminium industry is energy intensive and uses fossil fuels both for energy purposes and as reaction material. Additionally, the aluminium industry uses significant amounts of electricity. The electrolysis process in the primary production of aluminium is the most energy- and carbon-intensive process within the aluminium industry. The aim of this paper is to study the effects on primary energy use, greenhouse gas emissions and costs when three energy efficiency measures are implemented in the electrolysis process. The effects on the primary energy use, greenhouse gas emissions and costs are calculated by multiplying the savings in final energy use by a primary energy factor, emissions factor and price of electricity, respectively. The results showed significant savings in primary energy demand, greenhouse gas emissions and cost from the implementation of the three measures. These results only indicate the size of the potential savings and a site-specific investigation needs to be conducted for each plant. This paper is a part of a research project conducted in close cooperation with the Swedish aluminium industry.

Energy and carbon balance of materials used in a building envelope renovation

Construction and demolition waste (CDW) are a priority waste stream in EU’s polices, accounting for about 30% of all waste generated. At the same time, according to the EU energy-efficiency directive, existing buildings subject to significant renovation need to be upgraded in their thermal building envelope in order to meet higher energy performance standard. This involves additional building materials and hence increases the CDW generation. This study investigates the energy and CO2 emission balance of building envelope renovation when using different building materials, taking into account the production and end-of-life stages. The study is based on a Swedish case-study building assumed to be upgraded to the passive house standard. Benefits from waste recovering are considered, including construction and demolition wastes. The results show that the selection of building materials can significantly affect the primary energy and CO2 emission balances. Depending on the material alternative the end-of-life primary energy use and net CO2 emission can be reduced by 5%-21% and 2%-24%, respectively, compared to the initial primary energy use and net CO2 emission. Therefore, a careful material choice at the design stage, as well as an efficient waste management, can contribute to reduce primary energy use and CO2 emission associated with energy renovation of existing buildings.

Annual climate impact and primary energy use of Swedish transport infrastructure


 
 
 By 2045, Sweden is to have zero net emissions of greenhouse gases. To reach this goal, stakeholders involved in planning and construction of Swedish transport infrastructure aim to half their climate impact by 2030. Planning for emission reduction measures require network level studies showing environmental impacts of the infrastructure network. Previous studies do not allow assessment of current hotspots in the infrastructure network, which limits their relevance for decision-support in this question. The aim of this paper is to assess the current annual climate impact and primary energy use of Swedish transport infrastructure by using a methodological approach based on life cycle assessment. The scope includes new construction and management (operation, maintenance, and reinvestment) of existing roads, railways, airports, ports, and fairway channels. The annual climate impact was estimated to 2.8 million tonnes carbon dioxide equivalents and the annual primary energy use was estimated to 27 terawatt hours. Mainly road and rail infrastructure contributed to these impacts. Environmental hotspots of the infrastructure network were management of the infrastructure stock (particularly reinvestment of road and rail infrastructure) and material production (particularly production of asphalt, steel, and concrete). If climate targets are to be met, these areas are particularly important to address. Additional research on impacts of small construction measures, the size of biogenic carbon emissions (in standing biomass as well as soil carbon), and the use and impacts of asphalt for road construction and management would further increase the understanding of impacts related to Swedish transport infrastructure at the network level.
 (Note: an Erratum has been published to this paper in volume 20(2))
 
 

Comparative Life-Cycle Analysis of Building Materials for the Thermal Upgrade of an Existing Building

The existing building stock is estimated to need major renovations in the near future. At the same time, the EU energy-efficiency strategy entails upgrading the energy performance of renovated buildings to meet the nearly-zero energy standard. To upgrade existing buildings, two main groups of measures can be adopted: thermally-improved building envelope and energy-efficient technical devices. The first measure usually involves additional building materials for thermal insulation and new building cladding, as well as new windows and doors. A number of commercially-available materials can be used to renovate thermal building envelopes. This study compares the life-cycle primary energy use and CO2 emission when renovating an existing building using different materials, commonly used in renovated buildings. A Swedish building constructed in 1972 is used as a case-study building. The building’s envelope is assumed to be renovated to meet the Swedish passive house standard. The entire life cycle of the building envelope renovation is taken into account. The results show that the selection of building materials can significantly reduce the production primary energy and associated CO2 emissions by up to 62% and 77%, respectively. The results suggest that a careful material choice can significantly contribute to reduce primary energy use and CO2 emissions associated with energy renovation of buildings, especially when renewable-based materials are used.