Unit Energy Output Research Articles

Enhanced compression heat recovery of coupling thermochemical conversion to trigenerative compressed air energy storage system: Systematic sensitivity analysis and multi-objective optimization

Compressed air energy storage system has been considered as a promising alternative solution for stabilizing the electricity production driven by intermittent renewable energy sources. However, the inefficient utilization of thermal energy within the compressed air energy storage system hinders the efficient operation of system. Therefore, a novel trigenerative system integrated compressed air and chemical energy storage system is introduced in this study. The proposed system transforms the compression heat to the syngas in the form of chemical energy to achieve energy level upgradation during the charging process, and recuperates the thermal energy at the exit of the gas turbine to increase the inlet temperature of the compressed air for electricity enhancement during the discharging process. The residual heat during the operation process is then conducted for producing cooling and heating outputs simultaneously based on the law of energy cascade utilization. A systematic parametric analysis is carried out to investigate the effects of critical parameters on system comprehensive performance. Furthermore, the multi-objective optimization is employed to find the optimal trade-off among the thermodynamic performance, economic attractiveness and environmental friendliness of the proposed system. The parametric analysis indicates that the operating parameters of air compressor and gas turbine affect the performance indicators of thermodynamic and economic significantly. Moreover, at the best trade-off solution selected by the TOPSIS method, the system reaches 42.96 % of exergetic round trip efficiency, 105.28 $/MWh of levelized cost of energy and 206.94 kg/MWh of CO2 emission per unit energy output.

The Impact of Energy Tax on Carbon Emission Mitigation: An Integrated Analysis Using CGE and SDA

By originally integrating the structural decomposition analysis (SDA) into a computable general equilibrium (CGE) model, this paper simulates and analyzes the impact and mechanism of energy taxes on carbon emissions. Changes in carbon dioxide emissions, energy consumption structure, and other macroeconomic variables are investigated under different pre-set scenarios. The conclusion shows that the imposition of an ad valorem energy tax will indeed impact the production and consumption of enterprises. A higher tax rate leads to more pronounced reductions in carbon dioxide emissions. The carbon intensity effect is the dominant factor driving national carbon emissions and carbon emission intensity decline. Although the production structure effect and final demand effect play a role, their influences are relatively weak. While levying energy taxes, subsidies for personal income tax or corporate production tax can achieve double dividends. The progress of energy utilization technology is capable of increasing unit energy output and easing the negative impact of energy tax collection, and the gross national product may rise rather than fall. Under this circumstance, the production structure effect will play a greater role because the total demand coefficients of various industries for energy industry products will further decline. Only by levying energy taxes on coal and oil, exempting energy taxes on natural gas, or using energy tax revenue to subsidize investment in the natural gas industry can the government optimize the energy consumption structure. Subsidies will boost final demand for the natural gas mining and processing industry and increase the consumption share of natural gas, a cleaner energy source than coal and oil, which is critical in the current energy transition process.

The greenhouse gas removal potential of bioenergy with carbon capture and storage (BECCS) to support the UK's net-zero emission target

The UK is the first major economy to legislate the reduction of all GHG emissions to net-zero. Greenhouse gas removal (GGR) approaches are likely to be required to support the 2050 net-zero target by offsetting residual emissions from ‘hard-to-abate’ sectors. Bioenergy with carbon capture and storage (BECCS) is investigated as one technical solution for GGR. This research used process modelling and lifecycle assessment to identify the GGR potential of three BECCS supply chains. Results show that the BECCS supply chains have significant GGR potential with net-negative emissions as CO2e between −647 and −1137 kg MWh−1. Emissions were compared per unit energy output, biomass and area required for each supply chain to assess the GGR potential and BECCS sustainability implications. The large-scale BECCS supply chain features robust technologies with high capacity factor. It produces the greatest electricity generation and annual GGR, however, demands large amounts of biomass raising potential sustainability issues. The medium-scale (CHP) BECCS provides the greatest GGR potential per energy due to its higher energy efficiency. Limitations are a low capacity factor, energy demand-supply balance and non-existent decentralised CCS infrastructure. The (hydrogen) BECCS supply chain is more versatile, producing hydrogen with the potential to support the decarbonisation of not just power, but heat and transport sectors. The GGR potential sits in the middle and has greater benefits from a biomass sustainability perspective, yet, hydrogen infrastructure is not established, and costs remain uncertain. The relative performance of alternative BECCS supply chains should consider direct links between CO2 removal and sustainable biomass and land use, as well as GGR potential.

Energy Analysis and Emissions of Greenhouse Gases of Pomegranate Production in Antalya Province of Turkey

In this study, energy use patterns and the functional relationship between energy inputs and output for pomegranate production were investigated in Antalya province in Turkey. It further objective to identify greenhouse gas (GHG) emissions in pomegranate production. Data were obtained from 75 farms using face-to-face interview method. The results indicated that 50,605.5 MJ ⋅ ha−1 of total energy input was required for 76,252.3 MG ⋅ ha−1 pomegranate energy output. 1.51 unit energy output was provided by using 1 unit energy input. 1 unit energy output and 1 kg pomegranate require 0.66 unit and 2.57 MJ energy input, respectively. The average CO2 emission amounts were also calculated to be 1.73 t CO2 per hectare and 88.1 kg CO2 per 1000 kg pomegranate production. Electricity, fertilizers and pesticides were the highest contributors to GHG emissions. Both total energy input usage and GHG emission amounts have been found to be decreasing as the farm size increases. Increasing scale of pomegranates orchards will not only increase energy efficiency and productivity but also decrease environmental pollution and damages. The regression analysis revealed that, excessive use of machinery and fuel inputs results in a decline in energy production in pomegranate.

Bird and bat species' global vulnerability to collision mortality at wind farms revealed through a trait-based assessment.

Mitigation of anthropogenic climate change involves deployments of renewable energy worldwide, including wind farms, which can pose a significant collision risk to volant animals. Most studies into the collision risk between species and wind turbines, however, have taken place in industrialized countries. Potential effects for many locations and species therefore remain unclear. To redress this gap, we conducted a systematic literature review of recorded collisions between birds and bats and wind turbines within developed countries. We related collision rate to species-level traits and turbine characteristics to quantify the potential vulnerability of 9538 bird and 888 bat species globally. Avian collision rate was affected by migratory strategy, dispersal distance and habitat associations, and bat collision rates were influenced by dispersal distance. For birds and bats, larger turbine capacity (megawatts) increased collision rates; however, deploying a smaller number of large turbines with greater energy output reduced total collision risk per unit energy output, although bat mortality increased again with the largest turbines. Areas with high concentrations of vulnerable species were also identified, including migration corridors. Our results can therefore guide wind farm design and location to reduce the risk of large-scale animal mortality. This is the first quantitative global assessment of the relative collision vulnerability of species groups with wind turbines, providing valuable guidance for minimizing potentially serious negative impacts on biodiversity.

Spent Nuclear Fuel and Graphite Management for Salt-Cooled Reactors: Storage, Safeguards, and Repository Disposal

The fluoride salt–cooled high-temperature reactor (FHR) is a new reactor type that combines the graphite-matrix coated-particle fuel and graphite moderator from high-temperature gas-cooled reactors (HTGRs) with a clean liquid fluoride salt coolant. No FHR has yet been built. The proposed fuel cycle is a once-through fuel cycle—essentially identical to that of HTGRs. There is the option of adopting closed fuel cycles. Relative to light water reactor (LWR) spent nuclear fuel (SNF), all graphite-matrix coated-particle SNFs share the common characteristics of superior proliferation resistance and long-term performance as a waste form in a geological repository. The allowable HTGR and FHR SNF storage temperatures are much higher than allowable LWR SNF storage temperatures. These SNF characteristics are (a) a consequence of the high-temperature fuel form with a graphite matrix and SiC coating of the fuel microspheres and (b) to a first-order approximation independent of the reactor type in which the fuel is used.There are differences. The FHR reactor core power density is four to ten times higher than in an HTGR, so the short-term decay heat of the SNF per unit volume upon discharge is four to ten times higher. The volume of FHR SNF is one-half to one-third that of an HTGR per unit energy output because (a) the salt provides some neutron moderation thus reducing the carbon-to-uranium ratio of the fuel and (b) the economic optimization with higher power densities increases the fuel loading. The FHR SNF volume is about four times that of a LWR per unit of electricity. The coolant generates significant tritium that is partly absorbed by the graphite and can be partly desorbed at higher temperatures. Last, any residual solid salt coolant with the SNF at low temperatures can undergo radiolysis with the potential generation of fluorine gas. The presence of the salt coolant on the SNF and graphite moderator will require treatment, removal of residual coolant salt, or demonstration that the small quantities of radiolysis products of frozen salt do not impact long-term performance of storage or disposal facilities.

Assessment of criticality and burn up behavior of candu reactors with nuclear waste trans uranium fuel

Large quantities of nuclear waste plutonium and minor actinides (MAs) have been accumulated in the civilian light water reactors (LWRs) and CANDU reactors. These trans uranium (TRU) elements are all fissionable, and thus can be considered as fissile fuel materials in form of mixed fuel with thorium or nat-uranium in the latter. CANDU fuel compacts made of tristructural-isotropic (TRISO) type pellets would withstand very high burn ups without fuel change.As carbide fuels allow higher fissile material density than oxide fuels, following fuel compositions have been selected for investigations: ① 90% nat-UC + 10% TRUC, ② 70% nat-UC + 30% TRUC and ③ 50% nat-UC + 50% TRUC. Higher TRUC charge leads to longer power plant operation periods without fuel change. The behavior of the criticality k∞ and the burn up values of the reactor have been pursued by full power operation for > ∼12 years. For these selected fuel compositions, the reactor criticality starts by k∞ = 1.4443, 1.4872 and 1.5238, where corresponding reactor operation times and burn up values have been calculated as 2.8 years, 8 years and 12.5 years, and 62, 430 MW.D/MT, 176,000 and 280,000 MW.D/MT, with fuel consumption rates of ∼16, 5.68 and 3.57 g/MW.D respectively. These high burn ups would reduce the nuclear waste mass per unit energy output drastically. The study has show clearly that TRU in form of TRISO fuel pellets will provide sufficient criticality as well as reasonable burn up for CANDU reactors in order to justify their consideration as alternative fuel.

Utilization of TRISO fuel with reactor grade plutonium in CANDU reactors

Abstract Large quantities of plutonium have been accumulated in the nuclear waste of civilian LWRs and CANDU reactors. Reactor grade plutonium and heavy water moderator can give a good combination with respect to neutron economy. On the other hand, TRISO type fuel can withstand very high fuel burn-up levels. The paper investigates the prospects of utilization of TRISO fuel made of reactor grade plutonium in CANDU reactors. TRISO fuels particles are imbedded body-centered cubic (BCC) in a graphite matrix with a volume fraction of 68%. The fuel compacts conform to the dimensions of CANDU fuel compacts are inserted in rods with zircolay cladding. In the first phase of investigations, five new mixed fuel have been selected for CANDU reactors composed of 4% RG-PuO 2 + 96% ThO 2 ; 6% RG-PuO 2 + 94% ThO 2 ; 10% RG-PuO 2 + 90% ThO 2 ; 20% RG-PuO 2 + 80% ThO 2 ; 30% RG-PuO 2 + 70% ThO 2 . Initial reactor criticality ( k ∞,0 values) for the modes , , , and are calculated as 1.4294, 1.5035, 1.5678, 1.6249, and 1.6535, respectively. Corresponding operation lifetimes are ∼0.65, 1.1, 1.9, 3.5, and 4.8 years and with burn ups of ∼30 000, 60 000, 100 000, 200 000 and 290 000 MW d/tonne, respectively. The higher initial plutonium charge is the higher burn ups can be achieved. In the second phase, a graphical-numerical power flattening procedure has been applied with radially variable mixed fuel composition in the fuel bundle. Mixed fuel fractions leading to quasi-constant power production are found in the 1st, 2nd, 3rd and 4th row to be as 100% PuO 2 , 80/20% PuO 2 /ThO 2 , 60/40% PuO 2 /ThO 2 , and 40/60% PuO 2 /ThO 2 , respectively. Higher plutonium amount in the flattened case increases reactor operation lifetime to >8 years and the burn up to 580 000 MW d/tonne. Power flattening in the bundle leads to higher power plant factor and quasi-uniform fuel utilization, reduces thermal and material stresses, and avoids local thermal peaks. Extended burn-up grade implies drastic reduction of the nuclear waste material per unit energy output for final waste disposal.

Comparison of energy and greenhouse gas balances of biogas with other transport biofuel options based on domestic agricultural biomass in Finland

Biofuels have been promoted as a way to reduce greenhouse gas (GHG) emissions, but it is questionable whether they indeed do so. The study compared energy and GHG balances of transport biofuels produced in Finnish conditions. Energy and GHG balances were calculated from a life cycle perspective for biogas when timothy-clover and reed canary grass silages and green manure of an organic farm were used as a raw material. The results were compared with published data on barley-based ethanol, rape methyl ester (biodiesel) and biowaste-based biogas. The energy input for biogas was 22–37% of the output depending on the raw material. The GHG emissions from field-based biogas were 21–36% of emissions from fossil-based fuels. The largest energy input was used in the processing of the biofuels while most of the greenhouse gases were emitted during farming. The GHG emissions of the field-based biogas were emitted mainly from fuels of farming machinery, nitrous oxide (N2O) emissions of the soil and the production of ensiling additives. The energy efficiency was most sensitive to the methane yield, and GHG emissions to the N2O emissions. Biogas had clearly lower energy input and GHG emissions per unit energy output than domestic barley-based ethanol and biodiesel.;

Co-firing coal with rice husk and bamboo and the impact on particulate matters and associated polycyclic aromatic hydrocarbon emissions

The potential of co-firing rice husk and bamboo with coal was studied in a bench-scale pulverized fuel combustion reactor. Experimental parameters including biomass blending ratio in the fuel mixture, biomass grinding size, excess air ratio and relative moisture content in the biomass were investigated. Particulate Matters in the forms of PM 10, PM 2.1, ultra fine particles as well as the associated Polycyclic Aromatic Hydrocarbons (PAHs) emissions were evaluated. An operation range between 10% and 30% of biomass to coal ratio was found to be the optimum range in terms of minimum pollutant emissions per unit energy output. Co-combustion of coal with biomass seemed to have the effect of moving the fly-ash in PM 2.1 to a larger size range, but increasing the number counts of the ultra fine particles. It was noted that the much higher volatile matter content in the biomass fuels has played a key role in improving the combustion performance in the system. However, slagging, fouling and formation of clinker could be the issues requiring attention when using biomass co-combustion in conventional boilers.

Water Use in Renewable and Conventional Electricity Production

Water withdrawal and consumption from rivers, lakes and oceans in the United States is greatest in the electricity sector. Until recently, most analysis in this area has focused on thermoelectric and hydroelectric plants. However, proposals to increase renewable electricity sources have generated interest in the water impacts of solar, wind, geothermal and other renewables. The data are put on a per unit energy output basis for comparability. Renewables can have water use, per unit energy, comparable to conventional systems like coal and nuclear, when the entire cycle, including possible backup, is considered. Of those systems using freshwater, hydro has the highest water withdrawal and consumption.

The risk of producing energy

If risk is to be understood by the public, the sometimes abstruse numbers and calculation must be put into perspective. In terms of energy, the simplest way is to compare the risk per unit output for different forms of production. Previous studies have suggested that coal- and oil-fired electricity have higher overall risk than nuclear power, due primarily to the former’s air pollution effects. While newer, non-conventional energy forms such as solar and wind power may appear at first glance to be risk-free, this is not so. Because of the diluteness of the incoming energy, these non-conventional systems require large numbers of collectors per unit energy output. In turn, considerable quantities of steel, glass, copper, aluminium etc., are required, the production of which incurs occupational risk. In consequence, non-conventional systems can have substantial risk to health. The implications of this and Siddall's recent calculations on cost-benefit analysis are explored in terms of public policy.

Wind Power Potential in the Pacific Northwest

The Pacific Northwest is endowed with substantial resources of both hydro energy and wind energy for electrical power generation. The combination of these energy sources into an integrated and optimized system has the potential for supplying a major portion of the future energy requirements of Oregon, Idaho, Washington, western Montana and northeastern Nevada. The objective of the Pacific Northwest Wind Regional Energy Assessment Program (PNW WIND-REAP) is to identify areas of high wind-power density and develop an order-of-magnitude estimate of the maximum installed capacity, seasonal and annual energy and possible firm capacity available to the region from wind power when integrated with the Columbia River hydroelectric system. This paper presents an assessment of the potential resource and is not a recommended plan of implementation since obvious nontechnical considerations, i.e., institutional, environmental, aesthetics, etc., must be included in the final decision-making process before sites could be selected and technical specifications for wind energy conversion systems be prepared, ordered and installed. This resource assessment is being accomplished by installing wind data recording stations in those areas which, because of topography, signs of flagging or carpeted vegetation, and/or soil erosion provide evidence of strong or persistent winds. In. addition to national weather service stations, 33 active data stations, ranging from strip chart recorders to simple wind run recorders, are currently functional. The proven wind energy resources are concentrated in several regions in the Pacific Northwest, namely, the coastal zone of Oregon and Washington and the adjoining offshore waters, the Columbia River Gorge and adjacent ridge tops running from central Washington to just east of Portland, and portions of northeastern Nevada. Also, most of the higher elevations in the five-state area are believed to have significant wind energy potential, especially during the winter when the storm track moves over the Pacific Northwest. However, wind measurement programs are required in these mountains areas before reliable estimates of wind power potential can be made. Wind energy potential is examined in terms of the amount of time that power producing winds in the range 4.5–27.0 m s−1 occur. The resulting “effective wind power density” is examined on a seasonal basis at the various sites throughout the five-state area. The analysis indicates that there are large wind power resources not only during storms but also with the clear skies associated with high pressure to the northeast. In summer the dominant high pressure system over the Pacific results in substantial wind power along the coast and through the Columbia Gorge and to the cast. A preliminary indication of the energy production which could have been produced by a 1175 unit, 2140 MW rated, seven-site network in the Pacific Northwest during the period July 1976-February 1977 is 3.8 × 109 KWh. To obtain the lowest cost per unit energy output the wind turbine generator (WTG) unit should he sized according to the strength of the wind regime. However, a comparison of the cost per kilowatt-hour production for various size WTG ratings reveals that for a minor change in price, a sizable increase (or decrease) in energy output can be experienced.

FACTUAL INPUTS FOR ALLOCATION DECISIONS CONCERNING SCARCE WATER RESOURCES1

ABSTRACT: Factual inputs which may be useful for completing first‐order assessments to aid decision‐making on the allocation of scarce water resources are compiled. Water needs of major manufacturing industry groups and of minerals industries show wide variations in several measures of water use intensity. The chemicals and allied products and primary metals industries dominate the total water intake and consumptive water use by manufacturing industries. Consumptive use per employee for the petroleum and coal products industry group is nearly 2.5 times higher than that for any other industry group. Estimates of the water requirements per unit energy output for energy‐processing systems vary by as much as an order of magnitude. Agricultural water use is larger than that of any other industry but water use for irrigation is not expected to increase significantly by the year 2020. In California, the production of crop calories and proteins per unit of irrigation water applied may vary by more than an order of magnitude. Crops which offer larger monetary returns per acre are irrigated most frequently.