Reduction Of Primary Energy Consumption Research Articles

Life-cycle assessment of bioenergy production systems from oilseed rape crops

This article is concerned with a life-cycle assessment (LCA) study of bioenergy production systems based on oilseed rape cultivation. In particular, the study compares the production of biodiesel via transesterification of rapeseed oil, power generation through diesel engines fuelled by raw vegetable oil, and power generation through steam power plants fuelled by the overall aboveground biomass. The results of the LCA study show that bioenergy systems based on power generation perform better than bioenergy systems based on biodiesel production. In particular, the best energy and environmental performance are achieved with steam power plants fuelled by the overall aboveground biomass, which allow a reduction of primary energy consumption by about 75 per cent, the greenhouse impact by about 60 per cent, and the acidification impact by about 52 per cent with respect to conventional power generation plants. A favourable energy and environmental profile can also be achieved by diesel power systems (DPSs) and biodiesel fuel systems (BFSs), especially if the straw is used for power generation. In particular, the primary energy saving is about 58 per cent for DPSs and 72 per cent for BFSs without any straw energy use and about 67 per cent and 74 per cent with straw energy use, respectively. Moreover, these systems allow a reduction of the greenhouse (by about 55—58 per cent) and acidification impacts (from 21 per cent to 38 per cent), except for the BFS without any straw energy use, which increases the acidification impact by about 42 per cent. The study also demonstrates that crop cultivation greatly affects the performance, owing to the use of fuels and fertilizers.

Analysis and optimization of CCHP systems based on energy, economical, and environmental considerations

Analysis of combined cooling, heating, and power (CCHP) systems is frequently based on reduction of operating cost without measuring the actual energy use and emissions reduction. CCHP systems can be optimized based on different optimization criterion such as: energy savings, operation cost reduction or minimum environmental impact. In this study, CCHP systems operated following the electric load (FEL) and the thermal load (FTL) strategies are evaluated and optimized based on: primary energy consumption (PEC), operation cost, and carbon dioxide emissions (CDE). This study also includes the analysis and evaluation of an optimized operational strategy in which a CCHP system follows a hybrid electric–thermal load (HETS) during its operation. Results show that CCHP systems operating using any of the optimization criteria have better performance than CCHP systems operating without any optimization criteria. For the evaluated city, the optimum PEC and cost reduction are 7.5% and 4.4%, respectively, for CCHP-FTL, while the optimum CDE reduction is 14.8% for CCHP-FEL. Results also show that the HETS is a good alternative for CCHP systems operation since it gives good reduction of PEC, cost, and CDE. This optimized operation strategy provides a good balance among all the variables considered in this paper.

Evaluation of CCHP systems performance based on operational cost, primary energy consumption, and carbon dioxide emission by utilizing an optimal operation scheme

Optimization of combined cooling, heating, and power (CCHP) systems operation commonly focuses only on energy cost. Different algorithms have been developed to attain optimal utilization of CCHP units by minimizing the energy cost in CCHP systems operation. However, other outcomes resulting from CCHP operation such as primary energy consumption and emission of pollutants should also be considered during CCHP systems evaluation as one would expect these outcomes can be subject to regulation. This paper presents an optimization of the operation of CCHP systems for different climate conditions based on operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDE) using an optimal energy dispatch algorithm. The results for the selected cities demonstrate that in general there is not a common trend among the three optimization modes presented in this paper since optimizing one parameter may reduce or increase the other two parameters. The only cities that show reduction of PEC while also reducing the CDE are Columbus, MS; Minneapolis, MN; and Miami, FL. For these cities the operational cost always increases when compared to the reference case consisting of using a vapor/compression cycle for cooling and natural gas for heating. On the other hand, for San Francisco and Boston, CCHP systems increase the CDE. In general, if CCHP systems increase the cost of operation, as long as energy savings and reduction of emissions are guaranteed, the implementation of these systems should be considered.

Hybrid-cooling, combined cooling, heating, and power systems

Combined cooling, heating, and power (CCHP) systems have the ability to optimize fuel consumption by recovering thermal energy from the prime mover of the power generation unit (PGU). Design of a CCHP system requires consideration, among other variables, of CCHP system components size and type. This study focuses on the analysis of hybrid-cooling, heating, and power (hybrid-cooling CCHP) systems that have an absorption chiller (CH) and a vapour compression system to handle the cooling load. The effect of the size of both cooling mechanisms is analysed in conjunction with the PGU size and efficiency. For better energy performance analysis simulations, results are presented based on the building-CCHP system primary energy consumption (PEC). Hybrid-cooling CCHP systems yield higher primary energy reduction than CCHP systems with an absorption CH alone. To account for the effect of climate conditions, hot and cold climates were considered by performing simulations for Tampa and Chicago weather conditions. The results are presented in tabular form to show the value of the PEC reduction as a function of the PGU size and efficiency, and the size of the absorption CH.

Thermal and environmental assessment of a passive building equipped with an earth-to-air heat exchanger in France

In France, where a division by 4 of the greenhouse gases emissions is aimed from 1990 to 2050, technical solutions are studied in order to reduce energy consumption while providing a satisfactory thermal comfort level in buildings. A two-dwelling passive building has been carried out in Formerie (North-West of France), complying the “Passivhaus” standard. This building, not yet monitored, has been modeled using the dynamic simulation software COMFIE, which is dedicated to building eco-design. In order to account for the implemented ventilation system, including a heat recovery unit and an earth-to-air heat exchanger, a specific model has been developed and integrated to COMFIE as a new module. In this article, this model is described first. In order to quantify the benefits brought by a passive design, the simulation results are presented for the passive house and a reference house complying with the French thermal regulation for buildings. The heating load and thermal comfort level of both houses are compared, showing for the passive design a tenfold reduction of the heating load and a clear reduction of summer discomfort. Finally, the environmental assessment – carried out with the life cycle assessment tool EQUER – shows the reduction in primary energy consumption, global warming potential and other impacts brought by the passive house design. Passive house appears to be an adequate solution to improve the environmental performances of buildings in the French context.

ORC technology for waste-wood to energy conversion in the furniture manufacturing industry

Exploitation of low and medium temperature thermal sources, in particular those based on biomass combustion and on industrial residual heat recovery, has been increasingly investigated in the last decades, accordingly to the growing interest towards reduction in primary energy consumption and environmental issues. Organic Rankine cycle technology allows designing power plants that are less demanding in terms of auxiliaries, safety systems, maintenance and operating costs when compared to conventional water steam power plants. To support the preliminary technical and economic design of this kind of plants in different contexts, a simulation code of part load and off-design operation of an organic Rankine cycle unit for combined heat and power has been developed. In the paper, taking the real situation of a furniture manufacturing factory as a starting point, it is shown how all energy flows occurring all year long inside the combined heat and power plant, can be estimated on the basis of the thermal user duty time profile, the available biomass flow rate and the adopted operation strategy. This information is the basis in order to correctly evaluate the energetic, economic and environmental advantages of the proposed technical solution, with respect to a particular context, as it is shown in the concluding part of the paper.

Applying sustainable technology for saving primary energy in the brewhouse during beer brewing

Wort boiling is the most energy intensive stage in the brewing process. For this reason considerable attention has been given to improve the efficiency of wort boiling systems. Alternative wort boiling technologies, such as low pressure boiling and high temperature wort boiling, have been studied in detail during the last decades, with a focus on the reduction of primary energy consumption. Recently, new boiling systems have been developed and commercialised. The new systems reduced the energy consumption still further and are all characterised by exerting a low thermal stress on the wort during boiling. In this review, an overview of wort boiling objectives, possibilities to reduce the thermal stress on wort and environmental aspects of wort boiling are discussed. Furthermore, recent wort boiling systems—i.e. dynamic low pressure boiling and boiling systems which are based on low thermal stress boiling in combination with volatile stripping (steam, film and vacuum stripping)—are given special attention.

CO2 Emission Reduction and Primary Energy Conservation Effects of Cogeneration System in Commercial and Residential Sectors Considering Long-Term Power Generation Mix in Japan

This paper proposes a comprehensive model to examine future CO2 emission reduction and primary energy conservation through the installation of a cogeneration system (CGS) in commercial and residential sectors of Japan considering its long-term power generation mix. With the development of a CGS model and a long-term generation mix model on cost minimizing basis, Japan’s prospective power generation structure is figured out and the potential of CO2 emission reduction and primary energy conservation by a CGS is evaluated. With considerable uncertainty remaining concerning various assumptions made for the model analysis, following results are identified. (1) In all fuel price scenarios in power plants, the installation of CGS in commercial and residential sectors accomplishes the reduction of primary energy consumption. (2) In a standard fuel price scenario, the installation of CGS in commercial and residential sectors achieves the reduction of CO2 emission. In a low fuel price scenario which is the case current fuel prices continue for the future, however, CO2 reduction effect becomes decreasing compared to the standard fuel price scenario because of the dominant generation share of a LNG fired plant and a LNG combined cycle in future generation mix and these less carbon intensive plants replaced by CGS. In the case where nuclear power plant becomes competitive and increases its share in future generation mix, CO2 emission from energy system conversely increases by installing CGS in comparison with before installing, because electric power generation of CGS gradually replaces a nuclear power plant. These results suggest that the CO2 reduction potential by CGS introduction is cautiously evaluated taking into consideration the future power plant construction program in Japan.

Cogeneration—the development and implementation of a cogeneration system for a chemical plant, using a reciprocating heavy fuel oil engine with a supplementary fired boiler

The contribution of cogeneration plants to a reduction in primary energy consumption will be important not only in lowering emissions to the atmosphere but also in cutting production costs by increasing the overall efficiency of fuel conversion to the electricity and heat used by process industries. This paper demonstrates the importance of the interactions of the utility needs of a process with the development and design of a cogeneration system to maximize fuel efficiency and achieve environmental compliance for a chemical plant. The cogeneration system in this project is based on a diesel cycle engine burning heavy fuel oil (HFO), driving an alternator and with an exhaust gas heat recovery boiler supplementary fired with either HFO or natural gas. The normal operation of the cogeneration plant is with the engine running at 95–100 per cent maximum continuous rating (MCR) with the supplementary firing of the boiler modulating to meet the process requirements for saturated steam at 10 barg. In addition to recovering waste heat from the engine exhaust gas (EEG), supplementary firing using the excess oxygen in the exhaust gas enables the process steam required by the plant to be produced without the loss of energy involved in heating combustion air. At the same time the reduced volume of oxygen available to the flame reduces peak temperature and NOx emissions, this being further enhanced by the phased combustion design of the burner. The technology demonstrated in this application is generally as used in gas turbine cogeneration cycles burning natural gas. The use of HFO in this instance necessitated the use of a reciprocating engine driven generator and the development of supplementary firing of the exhaust gases. The successful development of the technology enables this reciprocating engine based cogeneration system to be scaled up or, possibly more importantly, down utilizing HFO, natural gas or renewable derived liquid or gaseous fuels. Its implementation using spark ignition engine generators retrofitted to economic boilers may be one way general industry in the United Kingdom might meet its climate change levy (CCL) targets for energy reduction and help approach the government's carbon reduction requirements.

大規模蓄熱槽を有する地域冷暖房の環境負荷低減効果に関する研究 : 竣工後の実測データに基づく検討

Based on measurements of district heating and cooling (DHC) system, which was built using a plan focusing on maintaining temperature difference and increasing the quantity of effective thermal storage, the following results were shown ; 1) maintaining a temperature difference resulted in good COP of DHC system, and 2) an appropriate system design aided in the reduction of primary energy consumption.

流通式反応装置における液相メタノール合成反応速度の実験的測定

To achieve reduction of primary energy consumption and prevent deterioration of global environment, a liquid-phase methanol synthesis process was investigated to recover wasted or unused discharged heat from industrial sources for the thermal energy demands of residential and commercial areas. The chemical reaction rate of methanol synthesis by hydrogenolysis of methyl formate was measured using a plate-type of Raney copper catalyst in a reactor with circulating flow. The contents of methanol in the liquid were analyzed by gas chromatographs, then the reaction rate was calculated by the measured increases in methanol due to reaction. The reaction characteristics were investigated by carrying the experiments at various temperatures, flow velocities and at various catalyst development conditions. It was obtained that the reaction rate increases with the temperature due to the enhancement of activation of the catalyst and the increases of solubility of hydrogen gas in methyl formate. It increases also at higher flow velocity for the higher diffusion effect. The reaction rate showed little dependence on the catalyst thickness under the present experimental condition for the catalyst thickness ranging from 64 to 70μm.

Global climate and energy systems

Consensus exists that further environmental pollution and climate change could be prevented if energy systems' emissions are significantly reduced. But energy will remain one of the most active driving forces of social and economic progress over the whole 21st century. This predetermines the necessity and expediency for long-term energy studies. Global energy systems recently have started the transition path from systems based on fossil fuels, with limited and exhaustible resources, to systems using inexhaustible or renewable energy resources (fission and fusion, solar, wind, biomass, geothermal, etc.). It is difficult to foresee exactly how long this transition period will last, because the rates of transition will depend on many factors — of which the most important will be energy costs at the end-user and the systems' impacts on humans, biosphere, and natural environment. Two global energy scenarios (Dynamic-as-Usual and Enhanced Energy Efficiency and Conservation, with several options for each of the scenarios) until the middle of the next century are discussed in the paper. According to energy projections, energy demand in developed countries is likely to stay at the current level over the whole time period or may even slightly decline (it is quite possible that in some countries with very high per capita energy demand, the reduction of primary energy consumption will start even in the near future). The major part of the energy demand growth worldwide will be justified by the needs of developing countries to improve their economic and social position. It is expected that primary energy demand in developing countries will increase by a factor of 3–5 compared to today's level. The world primary energy mix will very much depend on development strategies applied over the next 50–60 years. If a strategy for massive prevention of global warming is to be required, the share of fossil fuels in primary energy consumption must be remarkably reduced (even down to 25% in case of a 60% CO 2 emission reduction until the middle of the next century as stated by IPCC). Electricity keeps its position as a most universal energy carrier in all sectors of end-use, including transportation. Environmental protection goals can be achieved with the most effective and less expensive ways through applying electric technologies. Therefore, a strong growth rate for electricity generation is projected in both regions — developed and developing countries. Even if radical steps are taken to prevent the impact of energy systems on global climate, the CO 2 accumulation in the atmosphere will not be stopped. At the best, we can speak only of postponing the doubling of carbon concentration in the atmosphere for a couple of decades in the longer future. Parallel efforts within other spheres of the human activity are required: first of all, to stop deforestation of tropical forests, enhance reforestation, and reduce emissions of other greenhouse gases which in total contribute about 50% to global warming. The transition to an accelerated CO 2 reduction policy will require about 4–5% of the world GNP spent on investments within energy systems, which is not significantly higher than today. However, the structure of investments must be drastically changed from energy production to energy conservation and savings. Large concerns exist in finding capital to provide these investments in developing countries because it will be hardly possible for them to accomplish energy/climate programs without strong assistance from the developed world. It would be naive to think that a global energy and climate change policy could be introduced without massive obligatory measures at the national and global levels. These measures should include policy actions, marketing guidelines, educational programs, financial mechanisms, and technology transfer. The realization of such a policy will require the creation of new institutional frameworks, with concerted efforts of all players on the international and national energy markets. However, there are still many unsettled questions that remain in global warming and in looking for effective response strategies.