Combined Heat And Power Production Research Articles

Technical, economic and environmental analysis of energy production from municipal solid waste

Four technologies are investigated which produce energy from municipal solid waste (MSW): incineration, gasification, generation of biogas and utilisation in a combined heat and power (CHP) plant, generation of biogas and conversion to transport fuel. Typically the residual component of MSW (non-recyclable, non-organic) is incinerated producing electricity at an efficiency of about 20% and thermal product at an efficiency of about 55%. This is problematic in an Irish context where utilisation of thermal products is not the norm. Gasification produces electricity at an efficiency of about 34%; this would suggest that gasification of the residual component of MSW is more advantageous than incineration where a market for thermal product does not exist. Gasification produces more electricity than incineration, requires a smaller gate fee than incineration and when thermal product is not utilised generates less greenhouse gas per kWh than incineration. Gasification of MSW (a non-homogenous fuel) is, however, not proven at commercial scale. Biogas may be generated by digesting the organic fraction of MSW (OFMSW). The produced biogas may be utilised for CHP production or for transport fuel production as CH 4-enriched biogas. When used to produce transport fuel some of the biogas is used in a small CHP unit to meet electricity demand on site. This generates a surplus thermal product. Both biogas technologies require significantly less investment costs than the thermal conversion technologies (incineration and gasification) and have smaller gate fees. Of the four technologies investigated transport fuel production requires the least gate fee. A shortfall of the transport fuel production technology is that only 50% of biogas is available for scrubbing to CH 4-enriched biogas.

An efficient linear programming algorithm for combined heat and power production

Combined heat and power (CHP) production is an increasingly important energy production technology. CHP production is usually applied in back pressure plants, where the heat and power generation follows a joint characteristic. A CHP system may also comprise separate heat and power production facilities. Cost-efficient operation of a CHP system can be planned using an optimisation model based on hourly load forecasts. A long-term optimisation model decomposes into thousands of hourly models, which can be formulated as linear programming (LP) problems. We model the hourly CHP operation as an LP problem with a special structure and present the specialised Power Simplex algorithm that utilises this structure efficiently. The basis can be organised as an identity matrix and a small block of non-zero coefficients. There are only a few different types of non-zero blocks, and extremely fast inversion procedures have been designed for each type. The performance of Power Simplex is compared with realistic models against a non-sparse tabular Simplex algorithm and the LP2 software based on the sparse Revised Simplex algorithm using the product form of inverse. At its best, Power Simplex performs from 21 to 190 times faster than the tabular Simplex. Power Simplex has been implemented as part of the EHTO NEXUS energy optimisation system, which is in commercial use at several Finnish energy companies.

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies. At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.

Management of fluctuations in wind power and CHP comparing two possible Danish strategies

Both CHP (combined heat and power production) and wind power are important elements of Danish energy policy. Today, approximately 50% of both the Danish electricity and heat demand are produced in CHP and more than 15% of the electricity demand is produced by wind turbines. Both technologies are essential for the implementation of Danish climate change response objectives, and both technologies are intended for further expansion in the coming decade. Meanwhile, the integration of CHP and wind power is subject to fluctuations in electricity production. Wind turbines depend on the wind, and CHP depends on the heat demand. This article discusses and analyses two different national strategies for solving this problem. One strategy, which is the current official government policy known as the export strategy, proposes to take advantage of the Nordic and European markets for selling and buying electricity. In this case, surplus electricity from wind power and CHP simply will be sold to neighbouring countries. Another strategy, the self-supply strategy, runs the CHP units to meet both demand and the fluctuations in the wind scheduling. In this case, investments in heat storages are necessary and heat pumps have to be added to the CHP units. Based on official Danish energy policy and energy plans, this article quantifies the problem for the year 2015 in terms of the amount of surplus electricity, and investments in heat pumps, etc. needed to solve the problem are calculated. Based on these results between the two different strategies, the conclusion is that the self-supply strategy is recommended over the official export strategy.

전기와 스팀의 동시생산에 대한 할당방법

Five allocation methods which are applied to the CHP (Combined Heat and Power Production) are compared and in the thermodynamic respect, feasibility based on real process data are investigated using these methods. Among these five allocation methods, allocations based on energy and economic value are not adapted to the CHP unit. Allocations based on empirical thermodynamic efficiencies of steam and electricity have no objective standards needed for deciding their efficiencies. The allocation method based on the ideal thermodynamic efficiency is simple, objective and thermodynamically reasonable.

98/02837 Research on production of oils and RDF from waste plastics: Aihara, T. et al. Tokyo-to Seiso Kenkyusho Kenkyu Hokoku, 1996 (Pub. 1997), 26, 114–122. (In Japanese)

Present EU trends strive to maximize the resources recovery from municipal solid waste thus minimizing the waste amount to be disposed off. Refuse-derived fuel (RDF) production is considered in some countries to be a priority solution even if current market scenarios and consumers scepticism at present limit its widespread utilization. In this work, a comparison has been carried out of two possible RDF utilization alternatives, with particular reference to territorial districts with low population density. After a brief introduction, in which current RDF combustion technologies are illustrated, two possible plant configurations are considered, one concerning only electric power production; the other one combined heat and power production (CHP), using heat for district heating purposes, resorting to two different architectures: single pass-out condensing turbine and back-pressure turbine. Possible application of these technologies to a case study is then proposed, referring to a central Italy mountain territory characterized by a low population density. Then, an economic evaluation has been carried out. Finally, a parametric study was performed in order to define acceptable values for the sale price of thermal energy and the effect on profitability of the incremental investment needed for the construction of a district heating network.

Mini-hydro power

The objective of this work is to compare anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) and sanitary landfilling for combined heat and power (CHP) production, using biogas. The comparison aims to select the most appropriate method using economic, environmental, technological and legal criteria. In the first scenario considered, the total amount of 50,000 Mg/y (SI unit Mg = metric ton = tonne) commingled MSW is disposed of in a sanitary landfill. In the second scenario, 40% of OFMSW from 50,000 Mg/y of commingled MSW is source-separated and subject to dry, thermophilic, anaerobic digestion. The remainder MSW and the digestate are disposed of in a sanitary landfill. A sensitivity analysis for 100,000 and 200,000 Mg MSW/y was also conducted. For both methods, the appropriate CHP engines were selected, the amounts of produced biogas, energy, GHGs, NOx to the atmosphere, leachate production and the total capital and operation costs were calculated. Regression equations for total cost, net present value and gate fee were developed and used for economic assessment. Based on energy, environmental and legal criteria, CHP production from anaerobic digestion is favored, compared to sanitary landfilling. Based on economic criteria, anaerobic digestion is selected for MSW productions exceeding 210,000 Mg/y and 150,000 Mg/y, for the cases the investment is implemented with own funds or draws 55% from public funds, respectively. For smaller MSW productions, sanitary landfilling is favored, respectively. Although the results are based on Greek economic conditions, the comparison methodology can be applied to other countries.

A comparative assessment of the energy and carbon balance of utilizing straw

There has been a recent growth of interest in the potential for using straw as an energy source to generate electricity and/or heat. The energy balance of this process is important as a measure of the sustainability of such an activity, while the CO 2 emitted and that saved by offsetting the need to produce energy by other means are also important, given the U.K.'s obligations to reduce CO 2 emissions. An existing methodology is adopted to calculate estimates of primary energy inputs and CO 2 outputs. Results of calculations are presented and considered in the context of their implications for potential uses of straw represented by four scenarios. One scenario is the use of straw as a fuel in commercial scale power only, heat only and combined heat and power (CHP) plants. Overall, CHP production provides the most favourable energy and CO 2 balances. Results are compared with those for alternative uses or disposal methods for straw, represented by other scenarios, and with those for producing electricity and/or heat by conventional means. Conclusions are drawn concerning the contributions to the energy and carbon balances of using straw as a fuel and recommendations are made for further work.

CHP production in integrated energy systems examples from five Swedish communities

With special emphasis on combined heat and power (CHP) in district heating systems, experience from local energy/environment planning in five Swedish communities is presented. The IEA-MARKAL model is used to describe the community energy system and to evaluate the role of different technologies in producing district heat. General conclusions are drawn about the competition between CHP and waste heat, and between CHP and end-use conservation. Other subjects discussed are local self-sufficiency in electricity, choice of technologies for CHP and emissions control, and the consequences of different emissions accounting schemes.

New power-production technologies: Various options for biomass and cogeneration

Bioenergy will be the most significant renewable energy source in the next few decades until solar- or wind-power production offers an economically attractive large-scale alternative. Structural changes are required in power production in the near future owing to concern for global warming. Separate power production from fossil fuels should be replaced as extensively as possible by a new highly efficient power-generation structure. In Scandinavia, as well as to some extent elsewhere in Europe, combined heat and power production (CHP) is widely used and is an efficient way to reduce CO 2 emissions. In CHP, the additional power capacity can be produced by using IGCC and diesel techniques, and a potentially double amount of electricity is obtained with a constant heat load. The Finnish JALO research programme focuses on these techniques in a wide spectrum of the thermochemical conversion programme. Basic and applied research as well as pilot activities has been carried out in research organizations and in industry in Finland. A sum of about ECU 9 million has been invested in the programme over the past five years. The first pilot and demonstration plants with solid-biomass IGCC technology will be put into operation by private enterprises in 1993. If the price of biofuels is competitive, these new technologies will probably be commercialized by the end of the 1990s. International co-operation within ECE JOULE and IEA has played an important role in the JALO programme.

CHP development: Impacts of energy markets and government policies

Combined heat and power production (CHP) and district heating (DH) helped achieve the energy policy objectives in the OECD. The high production conversion efficiency of CHP and DH considerably improved energy security. Favourable economic conditions combined with supporting government policies fostered their development. This paper analyses the historical developments of DH systems and CHP production by public utilities and private industry. Examples from various OECD countries illustrate the different conditions which have fostered progress, particularly during the 1970s and early 1980s. But since the mid-1980s economic conditions have changed and increased uncertainties about the economic viability of CHP and DH have emerged. In recent years, however, new initiatives have started to develop. A survey of current activities in OECD member countries shows that this renewed interest is primarily the result of environmental concerns related to energy production and use and, in particular, to the danger of global climate change. These issues are likely to be pivotal parameters for the further development of CHP and DH.

District heating in Sweden, 1972–1977

The oil crisis led to renewed interest in combined heat and power production (CHP) and consequently also in district heating. The studies of CHP which have been carried out in various countries indicate that no general conclusions can be drawn about the merits of CHP and that assessments are strongly dependent on local conditions. In the following Carl-Erik Lind gives an account of some of the salient features of the Swedish district heating systems and their development since 1972.