GJ Of Energy Research Articles

Prospects for carbon-neutral housing: the influence of greater wood use on the carbon footprint of a single-family residence

This paper examines the energy and carbon balance of two residential house alternatives; a typical wood frame home using more conventional materials (brick cladding, vinyl windows, asphalt shingles, and fibreglass insulation) and a similar wood frame house that also maximizes wood use throughout (cedar shingles and siding, wood windows, and cellulose insulation) in place of the more typical materials used – a wood-intensive house. Carbon emission and fossil fuel consumption balances were established for the two homes based on the cumulative total of three subsystems: (1) forest harvesting and regeneration; (2) cradle-to-gate product manufacturing, construction, and replacement effects over a 100-year service life; and (3) end-of-life effects – landfilling with methane capture and combustion or recovery of biomass for energy production. The net carbon balance of the wood-intensive house showed a complete offset of the manufacturing emissions by the credit given to the system for forest re-growth. Including landfill methane emissions, the wood-intensive life cycle yielded 20 tons of CO 2e emissions compared to 72 tons for the typical house. The wood-intensive home's life cycle also consumed only 45% of the fossil fuels used in the typical house. Diverting wood materials from the landfill at the end of life improved the life cycle balances of both the typical and wood-intensive houses. The carbon balance of the wood-intensive house was 5.2 tons of CO 2e permanently removed from the atmosphere (a net carbon sink) as compared to 63.4 of total CO 2e emissions for the typical house. Substitution of wood fuel for natural gas and coal in electricity production led to a net energy balance of the wood-intensive house that was nearly neutral, 87.1 GJ energy use, 88% lower than the scenario in which the materials were landfilled. Allocating biomass generation and carbon sequestration in the forest on an economic basis as opposed to a mass basis significantly improves the life cycle balances of both houses. Employing an economic allocation method to the forest leads to 3–5 times greater carbon sequestration and fossil fuel substitution attributable to the house, which is doubled in forestry regimes that remove stumps and slash as fuel. Thus, wood use has the potential to create a significantly negative carbon footprint for a house up to the point of occupancy and even offset a portion of heating and cooling energy use and carbon emissions; the wood-intensive house is energy and carbon neutral for 34–68 years in Ottawa and has the potential to be a net carbon sink and energy producer in a more temperate climate like San Francisco.

Energy and Air Emission Effects of Water Supply

Life-cycle air emission effects of supplying water are explored using a hybrid life-cycle assessment For the typically sized U.S. utility analyzed, recycled water is preferable to desalination and comparable to importation. Seawater desalination has an energy and air emission footprint that is 1.5-2.4 times larger than that of imported water. However, some desalination modes fare better; brackish groundwater is 53-66% as environmentally intensive as seawater desalination. The annual water needs (326 m3) of a typical Californian that is met with imported water requires 5.8 GJ of energy and creates 360 kg of CO2 equivalent emissions. With seawater desalination, energy use would increase to 14 GJ and 800 kg of CO2 equivalent emissions. Meeting the water demand of California with desalination would consume 52% of the state's electricity. Supply options were reassessed using alternative electricity mixes, including the average mix of the United States and several renewable sources. Desalination using solar thermal energy has lower greenhouse gas emissions than that of imported and recycled water (using California's electricity mix), but using the U.S. mix increases the environmental footprint by 1.5 times. A comparison with a more energy-intensive international scenario shows that CO2 equivalent emissions for desalination in Dubai are 1.6 times larger than in California. The methods, decision support tool (WEST), and results of this study should persuade decision makers to make informed water policy choices by including energy consumption and material use effects in the decision-making process.

An environmental impact assessment of exported wood pellets from Canada to Europe

Abstract There have been increased interests on exporting wood pellets from Canada to Europe to meet the increased demand on biofuels in European countries. The wood pellet industry in Canada, especially in the west coastal region, has grown at an annual rate of more than 20% averaged over last 5 years due to the steady supply of wood residues. This paper attempted to analyze the fuel consumption and air emissions associated with the wood pellet production in British Columbia and export to Sweden based on a streamlined life cycle analysis, starting from tree harvesting for wood residue production to the shipping of wood pellets from Vancouver to Stockholm in Sweden. The results showed that about 7.2 GJ of energy is consumed for each tonne of wood pellets produced and shipped to Europe, representing about 39% of the total energy content of the wood pellets. Among those energies consumed over the life cycle, about 2.6 GJ is associated with long-distance ocean transportation. The ocean transportation is also the major contributor to environmental and health impacts, followed by the pellet production processes. The fossil fuel content, which quantifies the amount of fossil fuel consumed over the life cycle, for exported wood pellets ranged from 19% to 35%, depending on whether natural gas or wood residue is used in the drying operation during the wood pellet production stage. To reduce the fossil fuel content and the environmental impacts, wood residues should be used in the drying operation and, if possible, local market should be explored to reduce the energy consumption associated with wood pellet transportation over long distances.

Embodied energy analysis of adobe house

In this paper an attempt has been made to develop a simple methodology to calculate embodied energy of the adobe house at Solar Energy Park, Indian Institute of Technology Delhi, New Delhi (28°35′N, 77°12′E) and its effect on the environment. The special feature of the adobe house is that, the whole house is constructed by using low energy intensive materials like soil, sand cow dung, etc. The embodied energy involved in construction of main structure, foundation, flooring, finishes, furniture, maintenance and electric work are 102 GJ, 214 GJ, 55 GJ, 5 GJ, 18 GJ, 59 GJ and 4 GJ, respectively. It is seen that the embodied energy involved in the maintenance of the adobe house (12% of total embodied energy) is significant. It has been found that approximately 370 GJ energy can be saved per year. The energy pay back time (EPBT) for the adobe house is 1.54 years. By using low energy intensive materials the mitigation of CO 2 in the environment is reduced by an amount 101 tonnes/year. The adobe house is more environmentally friendly house in comparison to conventional buildings.

An investigation of high operating temperatures in mechanical vapor-compression desalination

It is common practice to operate mechanical vapor-compression (MVC) seawater desalination systems at temperatures lower than 80°C. This study presents the detail engineering and economics of a MVC system operating at 172°C. The literature indicates that high overall heat transfer coefficients for the evaporator are possible at high temperatures with dropwise condensation on the steam side and pool boiling on the liquid side. Employing high operating temperature delivers the following advantages: (1) low compression work, (2) small latent heat transfer area, and (3) small compressor. These advantages potentially reduce operating costs and capital investment. The disadvantages follow: (1) pretreatment required to prevent fouling of heat exchangers, (2) careful selection of materials to prevent corrosion, and (3) larger sensible heat transfer area is required. A desalination plant is designed herein to produce 37,854 m 3/d (10 mil gal/day), which is financed with a 5%, 30-y municipal bond. To maximize energy efficiency, combined-cycle cogeneration is employed. For the US ($5.00/GJ energy), the product water selling price is estimated to be $0.49/m 3 ($1.86/thous gal). For the Middle East ($0.50/GJ energy) the product water selling price is estimated to be $0.38/m 3 ($1.44/thous gal). These are attractive prices relative to competing technologies.

Crop residues as soil amendments and feedstock for bioethanol production

Traditional solid fuels account for more than 90% of the energy supply for 3 billion people in developing countries. However, liquid biofuels (e.g., ethanol) are perceived as an important alternative to fossil fuel. Global crop residue production is estimated at about 4 billion Mg for all crops and 3 billion Mg per annum for lignocellulosic residues of cereals. One Mg of corn stover can produce 280L of ethanol, compared with 400L from 1Mg of corn grains; 1Mg of biomass is also equivalent to 18.5GJ of energy. Thus, 3 billion Mg of residues are equivalent to 840 billion L of ethanol or 56x10(9)GJ of energy. However, removal of crop residues exacerbates soil degradation, increases net emission of CO2, and aggravates food insecurity. Increasing the SOC pool by 1 Mg C ha(-1)yr(-1) through residue retention on soil can increase world food grain production by 24-40 million Mg yr(-1), and root/tuber production by 6-11 million Mg yr(-1). Thus, identifying alternate sources of biofuel feedstock (e.g., biofuel plantations, animal waste, municipal sold waste) is a high priority. Establishing biofuel plantations on agriculturally marginal or degraded lands can off-set 3.5-4 Pg Cyr(-1).

Comparing annual and perennial energy cropping systems with different management intensities

Given the political targets, it can be expected that in Europe, energy production from agricultural land will increase and that improved systems for its production are needed. Therefore, a four year field trial was conducted on one site in south-western Germany to compare and evaluate the biomass and energy yield performance of important energy crops. Six energy cropping systems with the potential to produce biomass for first and second-generation biofuels were selected. The systems were short rotation willow coppice, miscanthus, switchgrass, energy maize and two different crop rotation systems including winter oilseed rape, winter wheat and winter triticale. The two crop rotation systems were managed in either conventional tillage or no-till soil cultivation systems. The second test parameter was three different crop-specific nitrogen application levels. The performance of the energy cropping systems was evaluated by measuring the biomass yields and calculating the energy yields, as well as through an energy balance and nitrogen budget. Results show the superiority of the annual energy crop maize in dry matter yield (DMY) and primary net energy yield (PNEY = difference between the primary energy yield (DMY × lower heating value) and the energy consumption) performance with peak values at the highest N-application level of 19.1 t DM ha −1 a −1 and 350 GJ ha −1 a −1, respectively. The highest yielding perennial crop was miscanthus with 18.1 t ha −1 a −1 DMY and a PNEY of 277 GJ ha −1 a −1, followed by willow with 15.2 t ha −1 a −1 and 258 GJ ha −1 a −1, at the highest N-application level. Switchgrass showed the lowest yields of the perennial crops with 14.1 t ha −1 a −1 DMY at the highest N-application level. The yields of the two crop rotation systems did not differ significantly and amounted to 14.6 t ha −1 a −1 DMY of both grain and straw at the highest N-application level. Willow showed the significantly highest energy use efficiency (output (PNEY):input (energy consumption)-ratio) with 99 GJ energy output per GJ fossil energy input at the lowest N-application level (no fertilizer). The two crop rotation systems had the lowest energy use efficiency with 20 GJ GJ −1 for the production of total aboveground biomass. Energy maize gave the best energy yield performance but at a relatively high energy input, whereas willow and miscanthus as perennial energy crops combine high yields with low inputs. Results suggest that no-till systems had no negative impact on biomass and energy yields, but that there was also no positive impact on energy saving.

Life cycle comparison of fuel cell vehicles and internal combustion engine vehicles for Canada and the United States

The objective of this study is to put forward a full analysis of the impact of the difference between the Canadian and American energy realities on the life cycle of fuel cell vehicles and internal combustion engine vehicles. Electricity is a major type of energy used in the transportation sector. Electricity is needed in the production of feedstock of fuel, the production of the fuel, the production of the vehicle material and the assembly of the vehicles. Therefore, it is necessary to investigate the impact of the electricity mix difference between Canada and the United States. In the analysis, the life cycle of the fuel consists of obtaining the raw material, extracting the fuel from the raw material, transporting and storing the fuel as well as using the fuel in the vehicle. Four different methods of obtaining hydrogen were analyzed; using coal and nuclear power to produce electricity and extract hydrogen through electrolysis and via steam reforming of natural gas in a natural gas plant and in a hydrogen refueling station. It is found that fuel cell vehicle fuelled by hydrogen has lower energy consumption and greenhouse gas emissions than internal combustion engine vehicle fuelled by conventional gasoline except for hydrogen production using coal as the primary energy source in Canada and the United States. Using the Canadian electricity mix will result in lower carbon dioxide emissions and energy consumption than using the American electricity mix. For the present vehicles, using the Canadian electricity mix will save up to 215.18 GJ of energy and 20.87 t of CO 2 on a per capita basis and 26.53 GJ of energy and 6.8 t of CO 2 on a per vehicle basis. Similarly, for the future vehicles, using the Canadian electricity mix will lower the total carbon dioxide emissions by 21.15 t and the energy consumed is reduced by 218.49 GJ on a per capita basis and 26.53 GJ of energy and 7.22 t of CO 2 on a per vehicle basis. The well-to-tank efficiencies are higher with the Canadian electricity mix.

Nitrogen, energy and land use efficiencies of miscanthus, reed canary grass and triticale as determined by the boundary line approach

Abstract The quantities and use efficiencies of nitrogen (N) fertilizer and energy input are seen as important indicators for the environmental impact of the production of energy crops. On the other hand, the high targets set in Europe for the production of biofuels will require high energy yields and efficient use of available agricultural land. The aim of this study is to describe the N, energy and land use efficiencies in relation to the N supply, for the energy crops triticale ( Triticosecale Wittmack) – harvested as whole crop – reed canary grass ( Phalaris arundinacea L.) and miscanthus ( Miscanthus × giganteus ). Field trials in Southwest Germany (48–49°N latitude) were performed to measure the biomass and bioenergy yields at different N fertilizer levels. The nitrogen use efficiency (NUE), defined as the ratio of biomass yield to N supply (sum of soil NO 3 − –N and N fertilized) and the energy use efficiency (EUE) (net energy yield/energy input), were derived from data on biomass and bioenergy yields by the boundary line approach. For all three crops, NUE and EUE decreased with increasing N fertilizer rates. NUE and EUE were at all N and energy inputs highest for miscanthus and lowest for reed canary grass. At an N supply of 100 kg ha −1 a −1 , the NUEs of miscanthus, triticale and reed canary grass were 0.35, 0.14 and 0.11 t dry biomass/kg N, respectively. At an energy input of 10 GJ ha −1 , the EUEs for miscanthus, triticale and reed canary grass were 54, 26 and 13 GJ bioenergy per GJ energy input, respectively. The highest net energy yields (here used as indicator for the land use efficiency) of triticale and reed canary grass were harvested at the highest N fertilizer level of 140 kg N, with maximum values of 281 and 129 GJ ha −1 a −1 , respectively. These results show that for triticale and reed canary grass, the maximization of NUE, EUE and land use efficiency are conflicting. Only for miscanthus, the N, energy and land use efficiencies were simultaneously highest at the lowest N supply level. A maximum net energy yield of 590 GJ ha −1 a −1 was harvested from miscanthus. It was concluded that the best way to maximize resource use efficiency in biomass production is to choose for the production of the perennial C4 crop miscanthus, at those locations that are suitable for miscanthus production.

Life cycle analysis of a solar thermal system with thermochemical storage process

Solar energy itself is generally considered as environmentally friendly, nevertheless it is still important to take into consideration the environmental impacts caused by production of thousands of solar thermal systems. In this work the standard LCA methodology has been extended to analyse the total environmental impacts of a new more efficient solar thermal system SOLARSTORE during its whole life cycle. This system is being developed by a 5th Framework EC project. The LCA results show that to produce 1 GJ energy with SOLARSTORE system will result in global warming potential of 6.3–10 kg CO 2, acidification potential of 46.6–70 g SO 2, eutrophication of 2.1–3.1 g phosphate and photochemical oxidant of 0.99–1.5 g C 2H 4. The raw material acquisition and components manufacturing processes contribute 99% to the total environmental impacts. In comparison with traditional heating systems, SOLARSTORE system provides a considerably better solution for reduction of negative environmental impacts by using solar energy more efficiently.

Life-cycle assessment in the renewable energy sector

The Polish energy industry is facing challenges regarding energetic safety, competitiveness, improvement of domestic companies and environmental protection. Ecological guidelines concern the elimination of detrimental solutions, and effective energy management, which will form the basis for sustainable development. The Polish power industry is required to systematically increase the share of energy taken from renewable sources in the total energy sold to customers. Besides the economic issues, particular importance is assigned to environmental factors associated with the choice of energy source. That is where life-cycle assessment (LCA) is important. The main purpose of LCA is to identify the environmental impacts of goods and services during the whole life cycle of the product or service. Therefore LCA can be applied to assess the impact on the environment of electricity generation and will allow producers to make better decisions pertaining to environmental protection. The renewable energy sources analysed in this paper include the energy from photovoltaics, wind turbines and hydroelectric power. The goal and scope of the analysis comprise the assessment of environmental impacts of production of 1 GJ of energy from the sources mentioned above. The study will cover the construction, operation and waste disposal at each power plant. Analysis will cover the impact categories, where the environmental influence is the most significant, i.e. resource depletion, global warmth potential, acidification and eutrophication. The LCA results will be shown on the basis of European and Australian research. This analysis will be extended with a comparison between environmental impacts of energy from renewable and conventional sources. This report will conclude with an analysis of possibilities of application of the existing research results and LCA rules in the Polish energy industry with a focus on Poland's future accession to the European Union. Definitions of LCA fundamental concepts, its methodology and application are described in the ISO 14040-14049 series of standards. These standards have already been introduced in some countries, but in Poland they are still at the stage of translation into Polish. Nevertheless some companies in Poland try to assess how their products influence the environment and what are the possibilities of technology improvement in the existing production process reduce their environmental impact.

Use of membranes for energy efficient concentration of dilute streams

In the chemical-process industries, dilute streams containing valuable ingredients are generated in several unit operations. Mechanical vapor-recompression is the best available technology for vaporization that may be used for concentrating such dilute solutions. Energy consumption for vaporization by compression and membrane technology is 350 and 90 kJ/kg, respectively. In order to save additional energy by recycling water, this study explored the use of membranes for processing a hot feed (70–80°C) containing small amounts of food ingredients. Pilot tests report the effects of experimental parameters on membrane performance. The impact of pretreatment of the feed and membrane-cleaning procedures to maintain performance will also be discussed. Initial results indicate that the use of a membrane to pre-concentrate, prior to the final concentration with mechanical vapor recompression, has the potential to save significant amounts of energy. Furthermore, the use of membranes would increase plant capacity by reducing the load on the vapor-compression unit. In this study, it was estimated that a plant processing 15 metric tonnes of feed every day and using membrane technology for concentrating to twice the concentraiton would save about 2 GJ of energy.

Nuclear Hydrogen Production Based on Sulfuric Acid Decomposition Process

A thermochemical nuclear hydrogen producing process has been developed and evaluated from thermodynamics and engineering points of view. The cycle is based on sulfuric acid decomposition process developed earlier, which produces mechanical power using additional primary energy as well as excess process heat generated within the cycle. The sulfuric acid decomposition process has been closed using a sulfur dioxide electrochemical oxidizer cell and feasibility of its energy self-sufficient operation has been demonstrated. The first law efficiency of the cycle has been determined as 34.14 percent and the second law efficiency as 43.32 percent. It is found that the modified sulfuric acid decomposition section is improved by 14.8 percent compared to the basic process used in the sulfur family cycles. For a plant size producing 8.94 × 106 GJ H2 per year, the typical levelized costs of hydrogen are $20.15(1988) per GJ energy and $24.47(1988) per GJ exergy.

Exergy and engineering analyses of hybrid thermochemical solar hydrogen production

A hybrid thermochemical solar hydrogen producing process has been developed and evaluated using the first and second laws of thermodynamics. The cycle is based on sulfuric acid decomposition and the synthesis processes developed earlier. The process has been improved by producing mechanical power using additional primary energy as well as excess process heat generated within cycle. The thermal and exergetic efficiencies of a daily cycle have been determined as 58.24 and 35.80 per cent, respectively. For a plant producing 0.66 × 10 6 GJ H 2 per year, the typical levelized costs of hydrogen for 15.9% capital charge rate are 40.92$ (1988) per GJ energy and 49.72$ (1988) per GJ exergy.

A model for sericulture and milk production

With a view to increasing the annual output of edible nutrients (milk), employment generation and obtaining better economic returns per unit area under sericulture, a model was designed through the application of the integrated systems approach. By the application of this model, it is possible to produce 23·23 GJ edible energy and 266·33 kg edible protein from milk; 2975 man-days employment and Rs.30·11 profit per man-day labour input from 1 ha in a year. In contrast, the traditional system of rice cultivation in Southern India, with double cropping intensity, could generate 50·67 GJ energy and 244·00 kg protein from food grains, 288 man-days employment and only Rs.8·34 profit per man-day labour input from 1 ha in a year.

Prospects for improving the utilization of fuel and energy resources

In improving the effectiveness of the use of fuel-energy resources in the Ninth and the first 3 years of the Tenth Five-Year Plan, and having doubled the production of pig iron and tripled the production of steel and rolled products in this period, our plant saved 225,500 tons of comparison fuel, 223.4 million kWh of electric power, and 1.042 million GJ of energy. Analysis shows that 80% of the fuel savings and 82% of the electric power savings were the result of the introduction of technical measures. The most important of these measures are the following: