Cumulative Consumption Of Non-renewable Exergy Research Articles

Reducing the impact of wind farms on the electric power system by the use of energy storage

The deployment of wind power is rapidly growing worldwide. Intermittent, unpredictable availability of wind energy destabilizes the work of the whole power system, which causes additional consumption of resources. When fossil fuel power plants are affected by this phenomenon, they are forced to cycle (change their load) more often, which results in higher consumption of fuel. This negative effect, expressed by means of thermo-ecological cost (TEC) can be significant in comparison to the TEC of construction phase of wind turbines. TEC is defined as the cumulative consumption of non-renewable exergy connected with the fabrication of a particular product. Power plant cycling could be minimized by applying an energy storage system responding to variations in wind power availability. In the present work, several scheduling strategies for cooperation of an energy storage system with wind turbines are investigated. The effect is assessed in local and global balance boundaries. Employing energy storage reduces the energy losses in thermal power plants, but at the same time, energy losses appear in the storage itself. However, depending on the strategy of energy storage scheduling, in some cases the overall consumption of primary exergy in the whole system may be lower.

Exergetic and thermo-ecological assessment of heat pump supported by electricity from renewable sources

Abstract Heat pumps (HP) represent an attractive option as a heat source, since they utilise “free” ambient heat. However, as they need to be driven by electric energy, their ecological efficiency depends not only on their performance, but also on the energy mix used for electricity generation. Effectiveness of HP can be improved by applying renewable energy sources (RES) providing electricity to drive the system. In order to properly assess such a system, it should be evaluated within a global balance boundary reaching the level of primary resources. The authors propose the use of thermo-ecological cost (TEC) indices for exergo-ecological assessment. TEC is defined as cumulative consumption of non-renewable exergy connected with the fabrication of a particular product. TEC also includes additional consumption of non-renewable natural resources which results from the necessity of compensating environmental losses caused by rejection of harmful substances to the environment. Within the paper, a HP system has been analysed from the ecological point of view. The system consists of a heat pump driven by electricity, and photovoltaic panels or wind turbines as a basic source of electricity. The balance of electricity demand for HP is complemented by electricity from grid. To evaluate this system, real environmental data on solar radiation, wind and ambient temperature deciding on heat demand have been taken into account. The authors present the ecological benefits resulting from supporting heat pumps by electricity generated in RES. It has been demonstrated by comparing results obtained within local and global balance boundaries, that the second approach should be consequently applied when systems based on a mix of renewable and non-renewable energy are analysed, since the first approach may lead to misleading conclusions.

Analysis of life cycle thermo-ecological cost of electricity from wind and its application for future incentive mechanism

In this paper, we apply a life cycle thermoecological cost (LC-TEC) approach to evaluate the environmental performance of wind turbines with different capacities and performance characteristics. LC-TEC expresses the cumulative consumption of non-renewable exergy burdening the fabrication of the considered consumption of the product with the additional inclusion of necessity of compensating adverse environmental effects due to harmful waste products rejection. Differently, from what has been recently done in the literature on the environmental performance of wind turbines, where the attention has been mainly drawn by analysis of single turbine, we focus on the synthesis of the results for wind turbines with different capacities and the generalisation of the results under different environmental conditions.The selected functional unit for the comparison was 1 MJ of produced electricity, assuming a service lifetime equal to 20 years. Concerning the contribution analysis, the construction phase is the most intensive one for wind energy technologies with a share varying from 64 to 77% in the overall effect. Substantial differences in LC-TEC are observed for wind turbines of different capacity and different locations of the power plant. Results show that the LC-TEC of electricity significantly decrease while the turbine nominal power increases. For instance, for the average site, described by Weibull distribution parameters of mean wind speed of 5 m/s and shape coefficient 2, the TEC-LC for 1 kW micro wind turbine is estimated to be equal to 0.436 MJex/MJ, while for a larger, 2 MW one, fall in the range of 0.053–0.063 MJex/MJ. We found that a power function can successfully describe such a trend. Moreover, we observed considerable changes in the final results for different Weibull distribution parameters. Specifically, the LC-TEC differs significantly for the sites with lower mean wind speed and different shape factors.Finally, we propose the supporting system for wind energy basing on the LC-TEC and pro-ecological taxing. According to this concept, the power units with LC-TEC below unity are to be supported, and the proposed level of pro-ecological support (ExTAX – Exergy TAX) is proportional to the thermo-ecological cost.The obtained results of exergy supporting for wind energy technologies are applied in the Italian electricity market and compared with the existing financing system for wind energy based on green certificates and feed-in tariff system.

Pro-Ecological Exergy Tax of Electricity

The concept of the pro-ecological tax or support is proposed in this article. It could replace the existing subsidy mechanisms for renewable power technology or could represent the ecological taxes burdening the fabrication of consumer products based on nonrenewable resources, e.g., electricity from the conventional fossil fuel power plants. Moreover, the proposed concept for renewable power technologies could represent a new system of subsidy based on physical laws. The proposed pro-ecological tax or support is defined as proportional to the thermo-ecological cost (TEC). TEC expresses the cumulative consumption of nonrenewable exergy burdening the fabrication of the considered consumption of the product with the additional inclusion of necessity of compensating adverse environmental effects due to harmful waste products rejection. It is assumed that calculating new exergy tax or subsidy for electricity, the total cost burdening the final consumer remains the same. This principle determines the coefficient of proportionality between the cumulative consumption of nonrenewable exergy (TEC) and the value of the tax or subsidy. In the case of nonrenewable electricity generation, the TAX causes the largest price growth. The higher is the efficiency of power technology, and the lower is the TEC of fuel, the lower tax is provided. In this paper, the prices of electricity produced from renewable and nonrenewable resources are calculated, taking into account the unavoidable consumption of resources. The unavoidable exergy consumption is caused due to the power plant construction, which is distributed through the whole life cycle of the plant. Results of calculation of proposed subsidies are compared with the current Polish system for supporting renewable power technologies.

Thermo-ecological cost of hard coal with inclusion of the whole life cycle chain

Fossil fuels are still the dominant source of energy in most economic sectors worldwide, particularly in the electric power sector. The transformation and usage of primary energy are connected with various unfavorable environmental effects. Mainly they are as follows depletion of constrained resources of non-renewable energy, emission of harmful wastes to the environment, emission of GHG (greenhouse gasses). To investigate these effects variety of methods have been developed, the LCA (Life-Cycle Assessment) is one of them. It has emerged as a valuable decision-support tool for both policy makers and industry in assessing the cradle-to-grave impacts of a product or process. Despite many advantages of LCA, it is unfortunately characterized by the lack of inclusion of thermodynamics law, especially second law, which is the basic physical law deciding on the resource economy in any production process. In the paper, the LCA methodology together with TEC (Thermo-Ecological Cost) is proposed to apply for exergo-ecological evaluation of fossil fuels. TEC expresses the cumulative consumption of non-renewable exergy connected with the fabrication of any useful product with additional inclusion of the consumption resulting from the necessity of compensation for environmental losses caused by the removal of harmful substances to the environment. The calculations of TEC of coal are based on the material balances of the whole chain of the production process from mine to the end-user. Within the chain in the coal mine the following sub-processes have been distinguished: preparation of the coal deposit layer for exploitation, exploitation of coal deposits, mechanical processing and enrichment of coal, ventilation of coal mine, transport, energy management of coal mines, compressed air management in coal mines and utilization of methane released during mine exploitation. Besides the processes in the mine, the end use is investigated. For this reason, the different types of coal are assigned for typical users. The potentially negative influence of utilization of coal with inclusion from cradle to grave assessment are examined on the basis of TEC evaluation.

Application of life cycle thermo-ecological cost methodology for evaluation of biomass integrated gasification gas turbine based cogeneration

Biomass integrated gasification cogeneration is nowadays considered as one of the most attractive technologies for CO2 emission reduction and non-renewable fuel savings. The paper presents application of the Thermo-Ecological Cost (TEC), which expresses the cumulative consumption of non-renewable exergy, for examination of energy and environmental benefits of biomass energy conversion plant based on gasification technology and medium scale recuperative gas turbine. To express the total effect of considered energy conversion systems the TEC is supplemented with the data resulting from Life Cycle Analysis (LCA). Different available gasification technologies and configurations of a cogeneration plant are investigated. Atmospheric fluidized bed gasification (AFB), pressurized fluidized bed gasification (PFB) and allothermal gasification using pure steam as gasification agent (FICFB) are taken into account as well as simple and combined power cycles with the Mercury 50 Solar gas turbine. The results reveal that simple cycle with gas turbine and waste heat recovery water boiler offers better effects than combined cycle configuration. The best performance has been reported for pressurized gasification technology.

Thermo-ecological and exergy replacement costs of nickel processing

In this paper, an exergy analysis of nickel processing is performed through the application of two methodologies: TEC (thermo-ecological cost) and ERC (exergy replacement cost). The merging of both methodologies allows to have a complete assessment of non-fuel mineral processing. TEC evaluates the cumulative consumption of non-renewable exergy required to produce a unit of useful product from the raw materials contained in natural deposits, i.e. from the cradle to the market. It further splits the results into the fuel, mineral and emission components so as to show the exergy consumption resulting from each part, thereby identifying the types of resources that are being consumed in each step of the overall production process. A problem detected with the TEC was that the exergy associated with the mineral component was small compared to that of fuels. This is because the TEC traditionally uses the chemical exergy of substances in their assessment and fossil fuels eclipse any other raw material. In order to overcome such issue, the TEC has been complemented with the ERC. The latter accounts for the exergy required to produce minerals from a completely dispersed state to the original conditions in which they were originally found in nature, i.e. the exergy that one would consume to restore minerals from the grave to the cradle. Through ERC, the aim is to account for the dispersion problem associated with minerals, because the scarcer a mineral, the more exergy is associated with its replacement. Results show that when ERC is embedded into the TEC infrastructure, the impacts associated with mineral consumption are significantly greater. Accordingly, the inclusion of ERC into TEC allows for a more comprehensive consumption of non-fuel mineral resources, thereby providing better indications as to the achievement of a more sustainable production.

Fuel part and mineral part of the thermoecological cost

The thermoecological cost, expressing the cumulative consumption of nonrenewable exergy per unit of the considered useful product, may be divided into the fuel part and the mineral part. The fuel part may be eliminated by the utilization of renewable exergy carriers. The mineral part cannot be eliminated. The depletion of mineral resources leads to the necessity of utilization of more and more lean natural resources. The equation system determining both parts of the thermoecological cost is formulated. Two numerical examples are included. The first one is a simple demonstration example, the second is detailed and relates to the Polish energy system.

Influence of the pro-ecological tax on the market prices of fuels and electricity

The proposed pro-ecological tax should be proportional to the cumulative consumption of non-renewable natural exergy burdening the considered product. It should replace the existing value-added tax (VAT). The income of the state after introducing the new tax, should remain without any change. That principle determines the coefficient of proportionality between the cumulative consumption of non-renewable exergy and the value of the tax. The total value of the tax should be paid to the state after extracting the minerals and fuels from nature and importing the fuels and semi-finished products, then transferred to the subsequent products in a form of their elevated price. Hence, the tax is eventually paid by the consumers in the form of an elevated price of goods and services. The total income of the society should remain without any changes. The largest price increase will appear in the case of fuels and electricity. The prices of electricity produced from renewable resources are calculated too, taking into account the accompanying unavoidable consumption of non-renewable exergy for the construction of the power plant. The new VAT should enhance the economy of the most energy-consuming products, stimulate the mitigation of the total consumption level of the society and increase the application of the renewable energy resources.

Depletion of the non-renewable natural exergy resources as a measure of the ecological cost

The cumulative consumption of non-renewable exergy connected with the fabrication of particular products has been termed as their ecological cost. System of linear input–output equations determining the ecological costs has been formulated. The cogeneration processes have been considered using the principle of the avoided costs of fabrication of the products substituted by the by-products of the considered process. The ecological cost determined in a regional scope takes into account the ecological cost of the imported raw materials and semi-finished products. This quantities have been substituted by the economically equivalent export of own products. The deleterious effect of the rejection of waste products to the environment has been approximately determined by means of the monetary indices of harmfulness of waste products. It has been proved, that the ecological cost of human work cannot be introduced into the set of input–output equations. Exemplary calculations have been made for the products connected with the blast-furnace process. The influence of the injection of auxiliary fuels into the blast furnace on the ecological cost of pig iron has been analyzed too.

Iterative Method to Evaluate the Ecological Cost of Imported Goods

Ecological cost indices can be defined as the cumulative consumption of non-renewable exergy connected with the fabrication of particular products. This cumulative consumption should comprise the additional exergy consumption of non-renewable resources resulting from the necessity of compensating the deleterious effects of the rejection of waste products to the environment. Ecological cost indices can be calculated by means of the system of linear balance equations of ecological cost. Indices calculated in this way, within the regional system, take into account the ecological cost indices of imported raw materials and imported semi-finished products. It is difficult to build up a set of balance equations to determine the indices of imported goods. In this paper the author proposes an iterative method of evaluating the ecological cost of imported goods. The results of sample calculations are also presented. This paper was presented at the ECOS'01 Conference in Turkey July 4-6, 2001 and revised