Evaluation of the Environmental and Economical Advantages of Combined Heat and Power (CHP) at Production Units

Transcription

1 Evaluation of the Environmental and Economical Advantages of Combined Heat and Power (CHP) at Production Uts Mohammad Hosein Amrollahi 1*, Sima Rezvantalab 2 1 Electrical Engineering Faculty, Urmia Uversity of Technology 2 Chemical Engineering Faculty, Urmia Uversity of Technology P.O. Box 57155/419, Urmia, I.R. Iran, amrollahi_mh@yahoo.com Increase in distributed generation sources in the industries is the direct result of improvement in technology and the energy crisis over the world. Nowadays utilization of renewable energy resources and highly efficient systems especially including the combined heat and power (CHP) are quickly increasing all over the world. Thus, High efficiency and positive environmental aspects are of the excellent advantages of such systems. In this paper set of factors in order to evaluate the environmental advantages of distributed generation resources is introduced. Based on them a novel method for calculating the energy production cost is presented. In this method, a negative value is considered for each environmental emission according its damaging effects and the costs arising from their pollution as the additional costs are superimposed on the production cost of the systems producing such contaminators. 1. Introduction In recent three decades, the importance of the alternative fuel, issue of increasing energy efficiency and decreasing environmental pollution as well as tendency to use modern technologies especially using combined heat and power production (CHP) methods has been increased. The main reason for this approach is the rapid increscent in fuel costs. In this method two common form of energy i.e. electrical and thermal is produced insitu and the electrical and heat loses is mainly reduced. One of the tendency reasons toward CHP is the need for increase in the efficiency of electrical energy production systems and reduction in emissions (Acharya, et. al, 2006). This is because of the excessive increase in emissions by fossil thermal power plants which led into endorsement of Kyoto agreement by most of countries in order to decrease the amount of green house gases. The major costs of power plants normally are supposed to be costs of construction, installation and operation where the environmental costs usually are neglected. This causes a misunderstanding in actual production costs in concentrated power plants and distributed generation (Dixon, 2007). Both high demands of industries and simultaneous electrical and heat energy causes to spread need of CHP in industrial zones entire the world, Such as obviating the peak

2 power losses, extending the inactive defense, decreasing the network heavy load and etc. From the economical view point the gain to cost ratio of simultaneous method is 9 times larger than the recent common electricity production method (Saba Co. guidance textbook, 2010). Of course it should be noted that establishing such plants of simultaneous production capability is not economical if one doesn't consider the variety of industries and consumption patterns and tries to utilize this method without the economical computations and surveys (report of resource dynamic corporation and CSGI, 2001). 2. Introduction to Distributed Production Simultaneous production resources have the lower productive capacity in comparison with the great generators and huge plants but also they need lower cost of operation. Furthermore the connections of these production uts to the distribution networks possess lot of advantages and a profit that includes economical considerations in plants developments, reduction of the environmental pollution, high efficiency of these resources for power producing, enhance the quality of power transmission to clients, reduction in distribution networks losses, improving in voltage profile, liberating the network capacity. Energy conversion average efficiency is an index that is defined as an indicator of output active power ratio to the energy feed at generation uts and can be calculated by Equation (1): (1) Average efficiencies related to few distributed generation technologies are given also in table (1): Table 1: Efficiency of electrical energy production technologies Conventional electrical Distributed generation energy generation Power plants CHP Biomass Fuel Cell Wind Turbines % % % % % It can be seen from Table (1) that the average efficiency of distributed generation is higher than conventional technologies efficiency and thermal power plants (Catalog of CHP technologies). 3. Characteristic Factors of the Environmental Advantages of Distributed Generation About 80% of the world environmental pollution is the result of using fossil fuels. Hence, presenting the index factors for evaluating environmental advantages of energy

3 product and utilizing them in the field of decreasing of environmental pollution is of great important. These indexes can be categorized as following: Annual production amount of primary contaminators containg SO 2, NO 2, CO, PM 10 and NMVOC 5 resulted from the energy consumption Annual production amount of green house gases including CO 2, CH 4, N 2 O, HFC, PFC and SF 6 resulted from the energy consumption Annual, daily and hourly average concentration of the main contaminators including SO 2, NO 2, PM 10 and O 3 in a specific geographical region; The first and second indexes can be calculated by the using of emission density concept. This is given by the equation (2): (2) Where mi is the amount of emission from i th contaminator in g/h and W i is the production power in kw. Table (2) gives the amount of some pollutants from fossil plants and distributed resources (Sun, 2004). Table 2: Amount of pollutants from various electricity production technologies (g/kwh) Power Plants NO x CO 2 CO SO 2 Coal Convention Natural al power gas plants Oil Micro turbine Fuel cell Distributed Photo productions voltaic Wind energy The Cost of Distributed Generation by Considering Environmental Advantages Ramakumar et. al, 1993 has described that distributed generation are some resources which need high installation costs, low cost of operation and maintenance with low cost of fuel; thus the production costs without considering the environmental problem can be calculated as given below: n r(1 + r) C az Cd = ( )( ) + C n OM + Cf (3) (1 + r) k

4 C d indicates the production cost in 0.01$/kWh, n is the time of investment return that is normally equal to equipments average age, C OM the costs required to operation and maintenance in 0.01 $/kwh, r is the annual average rate in percent and C f is equal to fuel cost for production of 1 kwh electrical energy which is equal to zero for renewable resources. The costs needed to produce 1 kwh of the electrical energy by DG can be calculated by: r(1 + r) C C C C m az, i h = αi( )( ) + OM, i + f i = 1 (1 + r) ki (4) Equation (4) is valid for a combinational system containg m kinds of distributed generation technology and α i is the portion of each i th technology in total output power of the system. Equation (4) also is indicator of DG production costs without considering the related environmental advantages. The Environmental costs is usually divided into two parts including economical value of environmental resources that includes pollutions due to contaminators and excess use of natural resources, and disadvantages due to pollution. Considering environmental costs, the new mathematical model of the production cost is given as blow: r(1 + r) C C C C C m az, i h = αi( )( ) + OM, i + f + e i = 1 (1 + r) ki (5) Where C e shows environmental costs and is given by: Also V ei is the environmental value of i th contaminator in $/kg, m is number of contaminators, Qi is the pollution amount of i th contaminator and V i is the penalty cost due to i th contaminator which should be paid. The environmental cost due to 4 major emitted gases from the plants are CO, CO 2, NO x & SO 2 and the related costs can be calculated considering their effects on human body health and is added to the costs of plants (for produced gas amount). In this work the production costs of various technologies are compared with each other and offered in table3. Table 3: Standard values for gases ($/kg) CO CO 2 NO x SO Table3 shows the loss rate due to the pollutant gases. (6)

5 Table 4: Cost of emitted gases related to their environmental damages ($/kg) CO CO 2 NO x SO Table 4 is provided by knowing the values given in table3 and utilizing the presented mathematical method (Qian, et al, 2008). Table 5: Comparison of generation costs related to various types Generation type Installation costs ($/kwh) Production costs ($/kwh) Production costs by considering environmental issues ($/kwh) Thermal Diesel Wind turbine Micro turbine Fuel cell Photo voltaic Table 5 compares the cost of various electrical energy producing technologies. According to the information given in Table 5, the environmental effects of plants and adding the additional losses due to the emission of contaminators, can deduce that conventional thermal plants have no more chance for any investment; while the distributed production resources which use renewable energies for producing electricity have lowest production costs (Morvay, et. al, 2008). 5. Conclusion In this paper some factors are introduced for evaluating the environmental advantages of distributed productions. Moreover, a mathematical method is presented. In this method, a negative value is considered for each loss effects of the environmental contaminators and the expenditures due to their propagation as excessive costs are added to the production costs of the systems producing the contaminators. According to the results, considering the environmental effects of plants and adding the negative damages due to the emission of contaminators, one can infer that conventional thermal plants have no more chance for any investment; while the distributed generation resources which use renewable energies for producing electricity have lowest production costs. In manufacturing uts that it is possible to use heat recovery system, the CHP systems is recommended.

6 References Achaya, P. Mahat and N. Mithulananthan, 2008, An Analytical Approach for DG Allocation in Primary Distribution Network, Electrical Power and Energy Systems, 28, Assessment of Replicable Innovative Industrial Cogeneration Application, 2001, Prepared by Resource Dynamics Corporation and CSGI., Iran (in Persian). Catalogue of CHP Technologies, < accessed Ding Shuying, Zhang Qingyu and Guo Hui, 2007, A modelling Study on Environmental Costs of Firepower Generation Shanghai Environmental Science, 26(2): Dixon, R. K., 2007, Near-term, Low-Cost CO 2 Reductions: Combined Heat and Power Opportuty Power-Gen Europe, Madrid Spain. Environmental Protection Agency, 2008, Technology Characterization: Gas Turbines. Environmental Protection Agency, 2008, Technology Characterization: Reciprocating Engines. Qian K., Zhou C., Yuan Y., Shi X. and Allan M., 2008, Analysis of the environmental benefits of distributed generation Proc. IEEE Power Engineering Society General Meeting, 1-5. Ramakumar R, Butler N G, Rodriguez A. P and Venkata, S.S,1993, Economic aspects of advanced energy technologies, Proceedings of the IEEE, 81 (3): Sun Ke., 2004, Environmental cost analysis and research of different power plants Energy engineering, 23 (3): Morvay Z. K. and Gvozdenac D. D., 2008, Applied Industrial Energy and Environmental Management, IEEE PRESS.