Modelling renewable supply chain for electricity generation with forest, fossil, and wood-waste fuels

In this paper, a multiple objective model to large-scale and long-term industrial energy supply chain scheduling problems is considered. The problems include the allocation of a number of fossil, peat, and wood-waste fuel procurement chains to an energy plant during different periods. This decision environment is further complicated by sequence-dependent procurement chains for forest fuels. A dynamic linear programming model can be efficiently used for modelling energy flows in fuel procurement planning. However, due to the complex nature of the problem, the resulting model cannot be directly used to solve the combined heat and electricity production problem in a manner that is relevant to the energy industry. Therefore, this approach was used with a multiple objective programming model to better describe the combinatorial complexity of the scheduling task. The properties of this methodology are discussed and four examples of how the model works based on real-world data and optional peat fuel tax, feed-in tariff of electricity and energy efficiency constraints are presented. The energy industry as a whole is subject to policy decisions regarding renewable energy production and energy efficiency regulation. These decisions should be made on the basis of comprehensive techno-economic analysis using local energy supply chain models.     

Markal,a linear-programming model for energy systems analysis: Technical description of the bnl version

As part of a project to assess the value of new energy technologies, an international group of researchers created a linear-programming model of national energy systems. This model, MARKAL, is driven by useful energy demands, optimizes over several time periods collectively, and allows multiobjective analyses to be performed quite easily. We describe here the technical structure of the model, defining the functions determined when satisfying the model's relations and the parameters that must be supplied to give the model content.     

LCI (Life cycle inventory) analysis of fuels and electricity generation in Singapore

This article offers a unique three-stage approach in LCI analysis for generating the environmental profile of electricity generation in Singapore. The first stage focuses on fuels delivered to Singapore, next on electricity generated from various types of power production plants. The third stage integrates the entire life cycle study. The final gate-to-gate results show that the total CO₂ emissions from the national grid are 455.6 kg CO₂ per MWh without any loss in transmission and 467.0 kg CO₂ per MWh with 2.5% losses. The results for the entire cradle-to-gate energy production are: 586.3 kg CO₂ per MWh without considering any losses and 601.0 kg CO₂ per MWh with 2.5% transmission loss. For the rest of the LCI, the cradle-to-gate results (per MWh) are kg 0.19 CO (carbon monoxide), 0.06 kg N₂O (nitrous oxide), 1.94–1.99 kg NO_x (nitrogen oxides), 2.94–3.01 kg SO_x (sulphur oxides), 0.064–0.066 kg VOC (volatile organic compounds) and 0.078–0.080 kg PM (particulate matters). From gate-to-gate, the results are 0.12 kg CO, 0.0016 kg N₂O, 1.42–1.46 kg NO_x, 2.56–2.62 kg SO_x, 0.033–0.034 kg VOC and 0.067–0.069 kg PM. Emissions of CO₂ from energy generation, climate change mitigation and policies for energy security are also discussed.     

The importance of comprehensiveness in renewable electricity and energy-efficiency policy

Based on extensive research interviews and supplemented with a review of the academic literature, this article assesses the best way to promote renewable energy and energy efficiency. It begins by briefly laying out why government intervention is needed, and then details the four most favored policy mechanisms identified by participants: eliminating subsidies for conventional and mature electricity technologies, pricing electricity accurately, passing a national feed-in tariff, and implementing a nationwide systems benefit fund to raise public awareness, protect lower income households, and administer demand side management programs. Drawing mostly from case studies in the United States, the article also discusses why these policy mechanisms must be implemented comprehensively, not individually, if the barriers to renewables and energy efficiency are to be overcome.     

Technoeconomic analysis of electricity generation from wind energy in Kutahya,Turkey

Conventional energy usage has various environmental effects that cause global warming. Renewable energy sources are thus more favorable because they have nearly zero emission. Wind energy, among the various renewable sources, finds increasing usage, concurrent with developing technology. In addition, wind is an infinite energy source. In this study, the electricity-generation ability of Kutahya has been investigated. With this aim, wind data, from the measurement station located on Bunelek Hill, Kutahya, have been collected for a period of 36 months (July 2001–June 2004). From the collected data, the electricity generated has been calculated for different types of wind turbines. The calculations have been based on the electricity requirement of the main campus of the Dumlupinar University. Finally, the economic evaluation has been analyzed using life-cycle cost analysis. For the analysis of the economical aspects, the social and CO₂ costs have also been taken into account.     

Energy,exergy and economic analysis of industrial boilers

In this paper, the useful concept of energy and exergy utilization is analyzed, and applied to the boiler system. Energy and exergy flows in a boiler have been shown in this paper. The energy and exergy efficiencies have been determined as well. In a boiler, the energy and exergy efficiencies are found to be 72.46% and 24.89%, respectively. A boiler energy and exergy efficiencies are compared with others work as well. It has been found that the combustion chamber is the major contributor for exergy destruction followed by heat exchanger of a boiler system. Furthermore, several energy saving measures such as use of variable speed drive in boiler's fan energy savings and heat recovery from flue gas are applied in reducing a boiler energy use. It has been found that the payback period is about 1 yr for heat recovery from a boiler flue gas. The payback period for using VSD with 19 kW motor found to be economically viable for energy savings in a boiler fan.     

Engineering and optimization approaches to enhance the thermal efficiency of coal electricity generation in China

China has made improving the thermal efficiencies of its coal-fired power plants a national priority. Official data show that the average thermal efficiency was enhanced from 31.3% in 2000 to 33.2% in 2005 and 36.9% in 2010. This paper aims to assess the validity of China's claimed improvement, examine major responsible factors, and identify future improvement opportunities. Recognizable factors can account for about 80% of the reported progress in the 10th Five-Year Plan (2001–2005) and about 85% in the 11th (2006–2010) to largely verify the reported progress. Engineering approaches—especially replacing inefficient power units with more efficient ones—are the largest contributing factors, while optimization approaches—particularly electricity dispatch—remains inefficient in China. In 2010, the explainable efficiency improvement might have avoided around 500 million tons of CO₂ emissions. In comparison, although the United States was fairly static with most of its coal-fired power plants seriously outdated, it has more efficient electricity dispatch. In China's ongoing 12th Five-Year Plan (2011–2015), better dispatch patterns could be more important as opportunities for improvement through engineering approaches have been largely exhausted.     

Financial impact of energy efficiency under a federal combined efficiency and renewable electricity standard: Case study of a Kansas “super-utility”

Historically, local, state and federal policies have separately promoted the generation of electricity from renewable technologies and the pursuit of energy efficiency to help mitigate the detrimental effects of global climate change and foster energy independence. Federal policymakers are currently considering and several states have enacted a combined efficiency and renewable electricity standard which proponents argue provides a comprehensive approach with greater flexibility and at lower cost. We examine the financial impacts on various stakeholders from alternative compliance strategies with a Combined Efficiency and Renewable Electricity Standard (CERES) using a case study approach for utilities in Kansas. Our results suggest that an investor-owned utility is likely to pursue the most lucrative compliance strategy for its shareholders—one that under-invests in energy efficiency resources. If a business model for energy efficiency inclusive of both a lost fixed cost recovery mechanism and a shareholder incentive mechanism is implemented, our analysis indicates that an investor-owned utility would be more willing to pursue energy efficiency as a lower-cost CERES compliance strategy. Absent implementing such a regulatory mechanism, separate energy efficiency and renewable portfolio standards would improve the likelihood of reducing reliance on fossil fuels at least-cost through the increased pursuit of energy efficiency.     

Energy and exergy analysis of fossil plant and heat pump building heating system at two different dead-state temperatures

In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air source heat pump building heating system at two different dead-state temperatures. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for heat pump building heating system. Since energy and exergy demand are key parameters to see which system is efficient at what reference temperature, we did a study on the influence of energy and exergy efficiencies. In this regard, a commercial software package IDA-ICE program is used for calculation of fossil plant heating system, however, there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP (coefficient of performance) curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis at two different dead-state temperatures revealed that the ground source heat pumps with ambient reference have better performance against all ground reference systems as well as fossil plant (conventional system) and air source heat pumps with ambient reference.     

Technical,economic, and environmental analyses of the modernization of a chamber furnace operating on natural gas or hydrogen

The paper presents a technical, economic and environmental analyses of a chamber furnace used to heat the charge before forging. The energy efficiency of the furnace before the modernization was 18%, after the modernization it was 31% (partial modernization due to large financial outlays). Other variants were also analysed: complete modernization, the variant of furnace modernization with 30% hydrogen content in the gas and the variant with 100% hydrogen as fuel. The analyses showed that with the current gas price (0.025 EUR/kWh) and the price of emission allowances (nearly 60 EUR/MgCO₂) and 100 cycles/year, the difference in Net Present Value (NPV) before base variant and partial modernization is around 900,000 EUR and before base variant and full modernization is 1,200,000 EUR. The introduction of the gas and 30% of hydrogen co-combustion option versus the base scenario option for 150 cycles per year results in a NPV difference of at least 2 million EUR. The option of 100% hydrogen as a fuel is the most advantageous from the point of view of reducing CO₂ emissions - it is largely influenced by the rising prices of CO₂ emission allowances.     

Energy optimization in a pulp and paper mill cogeneration facility

Alarmingly low pulp prices in early 2009 left pulp and paper mills across North America desperate for any way to improve thin profit margins. One solution that continues to gain popularity among the industry is improved energy management systems for cogeneration systems, which use steam for two purposes – to provide heat for the pulping process and to generate electricity for sale to regional providers. This paper presents an energy optimization algorithm for use in a pulp and paper mill cogeneration system. The algorithm is applicable to a number of popular mill configurations, power sale contracts, and fuel purchasing scenarios. The method is also extended to address weather-dependent cooling limitations encountered by a mill cogeneration facility, in which case an iterative solution is proposed in order to maintain convexity of the optimization problem. Results are presented in the form of three case studies.     

Primary energy and economic analysis of combined heating, cooling and power systems

In this paper, the primary energy consumption and the economic viability of a combined heating, cooling and power (CHCP) system are derived. The focus is on small-scale applications in the range below 100 kW_H/70 kW_C/58 kW_el. CHCP is discussed between the boundaries of combined heating and power (CHP) and combined cooling and power (CCP) using a lumped parameter model. The method used is independent of a specific load profile for a building; only the full-load hours for heating and cooling are needed to predict the economic viability. German data is used for the example. A sensitivity analysis reveals the parameters with the highest impact on the primary energy consumption and the energy costs. The primary energy factors, the energy prices and the electric efficiency of the CHP are the dominating parameters. Increasing electricity prices favour the introduction of CHP and CHCP systems whereas increasing gas prices inhibit it. The energy cost analysis is extended to an economic analysis taking maintenance and investment costs into account. One result of this paper is a simple diagram which shows how many annual operation hours are needed for heating and cooling with CHCP to be more economical than a reference system.     

Method for a component-based economic optimisation in design of whole building renovation versus demolishing and rebuilding

AimThis paper presents a two-fold evaluation method determining whether to renovate an existing building or to demolish it and thereafter erect a new building.ScopeThe method determines a combination of energy saving measures that have been optimised in regards to the future cost for energy. Subsequently, the method evaluates the cost of undertaking the retrofit measures as compared to the cost of demolishing the existing building and thereafter erecting a new one. Several economically beneficial combinations of energy saving measures can be determined. All of them are a trade-off between investing in retrofit measures and buying renewable energy. The overall cost of the renovation considers the market value of the property, the investment in the renovation, the operational and maintenance costs. A multi-family building is used as an example to clearly illustrate the application of the method from macroeconomic and private financial perspectives.ConclusionThe example shows that the investment cost and future market value of the building are the dominant factors in deciding whether to renovate an existing building or to demolish it and thereafter erect a new building. Additionally, it is concluded in the example that multi-family buildings erected in the period 1850–1930 should be renovated.     

The energy demand and the impact by fossil fuels use in the Mexico City Metropolitan Area, from 1988 to 2000

Temporary variation for the demand of refining products which are used in the Mexico City Metropolitan Area (MCMA) is presented. Its consequent energy contribution is evaluated from 1988 to 2000. The annual estimation was integrated from a detailed inventory of fuels volume, so as the calculus of its respective energy equivalence. The fuel quality specifications, which have been required by regional Air Quality authority for controlling emissions to the atmosphere, are also presented for the same period. The evolution demand of fuels, in term of volume, quality and its energy contribution for this area, is compared with the national demand. On this regard, fuel pool differs in each bound and the demand along the same period has been increasing on both regions but at different rates, with 21% at MCMA and 31% countrywide. In 2000, the MCMA demanded 14% of the internal refining products volume sales, which represented 17% of the energy contribution to the country for those fuels. Likewise, the energy use coefficient (GJ per capita) was applied to compare this region with country trends. During 1996 and up to 2000, the MCMA presented slightly minor energy use per capita, than the rest of the country, and this period was distinguished also for using cleaner fuels and for obtaining improvements in air quality. On the other hand, MCMA and country greenhouse gases emissions will increase because of their fossil fuel dependence, so several mitigation measures must be implemented in the next decades.     

Efficient utilization of waste heat from molten carbonate fuel cell in parabolic trough power plant for electricity and hydrogen coproduction

Direct steam generating parabolic trough power plant is an important technology to match future electric energy demand. One of the problems related to its emergence is energy storage. Solar-to-hydrogen is a promising technology for solar energy storage. Electrolysis is among the most processes of hydrogen production recently investigated. High temperature steam electrolysis is a clean process to efficiently produce hydrogen. In this paper, steam electrolysis process using solar energy is used to produce hydrogen. A heat recovery steam generator generates high temperature steam thanks to the molten carbonate fuel cell's waste heat. The analytical study investigates the energy efficiency of solar power plant, molten carbonate fuel cell and electrolyser. The impact of waste heat utilization on electricity and hydrogen generation is analysed. The results of calculations done with MATLAB software show that fuel cell produces 7.73 MWth of thermal energy at design conditions. 73.37 tonnes of hydrogen and 14.26 GWh of electricity are yearly produced. The annual energy efficiency of electrolyser is 70% while the annual mean electric efficiency of solar power plant is 18.30%.The proposed configuration based on the yearly electricity production and hydrogen generation has presented a good performance.     

Woodland owners' attitudes towards energy from forest biomass in a carbon-intensive jurisdiction: Case study of Nova Scotia,Canada

The use of forest biomass in thermal generation processes has been recognized by the Government of Nova Scotia (NS) as one option that could help meet its renewable electricity goals (25% by 2015 and 40% by 2020). Over half of the woodland in NS is owned by small-private woodland owners (51%), indicating that they could significantly influence the future of NS forests and its potential use for energy purposes. This paper presents the results of a survey of small-woodland owners on their attitudes towards using energy from forest biomass. 489 small-woodland owners responded to mail-out surveys and 14 rural community members participated in three focus groups. Three major findings emerged. First, it was found that the acceptability of using forest products varied depending on multiple factors – the source of biomass, harvesting methods, and [predicted] end-use. Second, forest sustainability and keeping resources local were the two most important concerns amongst respondents. Finally, respondents felt that better collaboration with other stakeholders and education around the issues would be the best strategies for overcoming these concerns. The paper also highlights the barriers and drivers as perceived by the woodland owners as they relate to the possibility of using more biomass for energy in the future.     

Conceptual design and analysis of a novel system based on ash agglomerating fluidized bed gasification for co-production of hydrogen and electricity

In this paper, a novel system with ash agglomerating fluidized bed gasification and CO₂ capture to produce hydrogen and electricity is firstly designed in Aspen Plus. The newly-proposed system is composed of eight subsystems, namely air separation unit, gasification unit, water gas shift unit, Rectisol unit, CO₂ compression unit, Claus unit, pressure swing adsorption unit, gas and steam turbine unit. The thermodynamic performance and hydrogen to coal ratio of the new proposed system are investigated. The results demonstrate that the hydrogen to coal ratio, energy efficiency, net electricity power and exergy efficiency of the overall system for Yangcheng anthracite are 0.096 kg/kg, 46.52%, 1.71 MW and 43.92%, respectively. Additionally, the exergy destruction ratio and exergy efficiency of each subsystem are researched. More importantly, the influences of the oxygen to coal ratio, steam to coal ratio and coal types on the hydrogen to coal ratio, energy efficiency and exergy efficiency are also studied.     

Transient analysis and energy optimization of solar heating and cooling systems in various configurations

In this paper, a transient simulation model of solar-assisted heating and cooling systems (SHC) is presented. A detailed case study is also discussed, in which three different configurations are considered. In all cases, the SHC system is based on the coupling of evacuated solar collectors with a single-stage LiBr-H₂O absorption chiller, and a gas-fired boiler is also included for auxiliary heating, only during the winter season. In the first configuration, the cooling capacity of the absorption chiller and the solar collector area are designed on the basis of the maximum cooling load, and an electric chiller is used as the auxiliary cooling system. The second layout is similar to the first one, but, in this case, the absorption chiller and the solar collector area are sized in order to balance only a fraction of the maximum cooling load. Finally, in the third configuration, there is no electric chiller, and the auxiliary gas-fired boiler is also used in summer to feed the absorption chiller, in case of scarce solar irradiation.The simulation model was developed using the TRNSYS software, and included the analysis of the dynamic behaviour of the building in which the SHC systems were supposed to be installed. The building was simulated using a single-lumped capacitance model. An economic model was also developed, in order to assess the operating and capital costs of the systems under analysis. Furthermore, a mixed heuristic-deterministic optimization algorithm was implemented, in order to determine the set of the synthesis/design variables that maximize the energy efficiency of each configuration under analysis.The results of the case study were analyzed on monthly and weekly basis, paying special attention to the energy and monetary flows of the standard and optimized configurations. The results are encouraging as for the potential of energy saving. On the contrary, the SHC systems appear still far from the economic profitability: however, this is notoriously true for the great majority of renewable energy systems.     

The contribution of small hydro power stations to the electricity generation in Greece: Technical and economic considerations

Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18.5% to the fulfillment of the planet electricity generation. However, most locations in Europe appropriate for the installation of large hydro power stations have already been exploited. Furthermore, there is a significant local communities’ opposition towards new large power stations; hence, small hydro power stations remain one of the most attractive opportunities for further utilization of the available hydro potential. Greece and more precisely the country's mainland possesses a significant hydro-power potential which is up to now only partially exploited. In parallel, a large number of private investors have officially expressed their interest in creating small hydro power stations throughout the country, encouraged by the significant Greek State subsidy opportunities for renewable energy applications. However, up to now a relatively small number of projects have been realized, mainly due to decision-making problems, like the administrative bureaucracy, the absence of a rational national water resources management plan and the over-sizing of the proposed installations. Certainly, if the above problems are suitably treated, small hydro-power plants can be proved considerably profitable investments, contributing also remarkably to the national electricity balance and replacing heavy polluting lignite and imported oil. In the context of the above interesting issues, the present study reviews in detail the existing situation of small hydropower plants in Greece and investigates their future prospects as far as the energy, economic and environmental contribution are concerned.