Substitution Of Coal Research Articles

Fossil Fuel Substitution with Renewables for Electricity Generation – Effects on Sustainability Goals

The substitution of fossil fuel power plants with renewable units will lead to a profound reduction of CO2 emissions and will assist in evading the Global Climate Change. Using demand data from the electricity grid of Texas, this paper develops a scenario for the substitution of coal, at first, and of all fossil fuel power plants, secondly, in the entire State of Texas. Meeting the electricity demand of the grid with renewables, makes it necessary to develop significant energy storage capacity in addition to the renewable – wind and solar – installations. Because of the lower pant capacity factors of wind and solar units, the calculations show that significantly higher renewable power capacity must be built than the current capacity of the fossil fuel units to be substituted. Also, that a substantial fraction of the generated energy is lost in the storage-recovery processes. All these factors are expected to increase the price of electricity paid by the consumers. Ahis will have an impact on the less affluent segments of the population and – if ignored by national energy policies – will affect the goal to reduce inequality within and among countries.

Elasticity of substitution and technical efficiency: evidence from the US electricity generation

ABSTRACTThe implications of national or regional energy policies for technical efficiency and environmental outcomes in electricity generation depend on fossil fuel input substitution. This study uses state level data to examine fossil fuel (coal and natural gas) substitution in electricity generation under increased availability of natural gas in the United States. We observe that changes in elasticities of substitution from pre-2009 to post-2009 differ across states suggesting that the effects of increased availability of inexpensive natural gas on electricity generation have been spatially heterogeneous. We rely on the observed heterogeneity to assess the effects of fossil fuel input substitution on technical efficiency and CO2 emissions. The results reveal that state level elasticity of substitution between natural gas and coal has a positive effect on technical efficiency and a negative effect on CO2 emissions. Therefore, future policy design and analyses should reflect the implications for regional elasticities of fossil fuel substitution and associated environmental outcomes.

From Rio to Paris via Kyoto: How the Efforts to Protect the Global Climate Affect the World Energy Development

The aims of this work are to analyze the changes in the world power industry during the time after the adoption of the United Nations Framework Convention on Climate Change of 1992 and to assess the extent to which the commitments of the Kyoto Protocol of 1997 have been met and evaluate the prospects of implementing the tasks of the Paris Agreement of 2015. Based on data on the production and consumption of various kinds of energy and the emissions of greenhouse gases, primarily carbon dioxide, in 1990–2017, changes in the structure of the global energy consumption, trends in electric power generation, and the influence of different factors on the carbon dioxide emissions in power-generating enterprises are investigated. It is shown that the power industry, which is the main source of anthropogenic greenhouse gases (GHGs), is the most inertial branch of the economy in terms of its contribution to the reduction in GHG emissions. Thus, in the first 2008–2012 commitment period of the Kyoto Protocol, GHG emissions in the state parties to the protocol decreased by 7.6% compared the base year, while other GHG sources reduced the emission by 18%. The corresponding figures for the following 2013–2017 commitment period were 10.6 and 17.1%, respectively. The maximum reduction in the carbon dioxide emissions in the power industry resulted from an increase in the global average efficiency of the thermal power stations from 32% in 1990 to 36% in 2017; as a consequence, the cumulative decrease in the CO2 emissions in the world during the 1990–2017 period was approximately 22 billion t. The increase in the electric power generation at HPPs and NPPs resulted in a reduction in GHG emissions by 16.7 and 10.7 billion t, respectively. The substitution of coal and fuel oil by gas at thermal power stations facilitated reducing the emissions by 5.2 billion t, while the use of renewable energy sources for generation of electric energy resulted in a reduction of 1.1 billion t. The contribution of the carbon capture and storage technologies amounting to only 0.2 billion t is not noticeable so far.

Literature Review about Mainstream Economics and Biophysical Economics

The history of human culture can be viewed as the progressive development of new energy source and their associated conversion technologies. For example, the invention of steam engines and internal combustion engines, led to the substitution of coal and oil for animal power and firewood as the main sources of energy, and eventually led to the industrial revolution. As results, these developments increased the economic and life quality. There are so much study indicates that there is a strong correlation between energy and economic growth. The role of energy in the economic system has come in for much discussion. For now, some debate still continues about the relationship between energy and economic growth from different perspective.

Optimizing Nitrogen and Residue Management to Reduce GHG Emissions while Maintaining Crop Yield: A Case Study in a Mono-Cropping System of Northeast China

Reducing the use of nitrogen fertilizers and returning straw to field are being promoted in northeast China (NEC). In this paper, the agricultural production system model (APSIM) was applied to assess the long-term variations of crop yield and soil GHG emissions in a maize mono-cropping system of NEC, and the simulation results were combined with lifecycle assessment to estimate annual GHG emissions (GHGL) and GHG emission intensity (GHGI, GHG emissions per unit yield) of different agricultural practices. Under current farmers’ practice, emissions due to machinery input (including production, transportation, repair, and maintenance) and soil organic carbon (SOC) decline accounted for 15% of GHGL, while emissions from nitrogen fertilizer input (production and transportation) and direct N2O emissions from soil accounted for the majority (~60% of GHGL). Current farmers’ practice in terms of N application and residue management are nearly optimal for crop production but not for climate change mitigation. Reducing N input by 13% and increasing straw retention by 20% can maintain crop yield and SOC, and also reduce GHGL and GHGI by 13% and 11%, respectively. However, it is not feasible to incorporate the straw used as household fuel into soil, which could incur substantial fossil CO2 emissions of 3.98 Mg CO2-eq ha−1 resulting from the substitution of coal for straw. APSIM was successful in simulating crop yield, N2O emissions, and SOC change in NEC, and our results highlight opportunities to further optimize management strategies (especially for the nitrogen and straw management) to reduce GHG emissions while maintaining crop yield.

Environmental potential analysis of co-processing waste in cement kilns

The technology of waste co-processing in cement kilns has proven to be a reliable, efficient and convenient method of waste disposal (domestic and industrial). However, countries around the world face the following key barriers to the implementation of the technology of waste co-processing in cement kilns: fuzzy legislation, lack of financial support, public acceptance, etc. These barriers can be partially eliminated by the measures proposed in this study.In addition, waste sorting and processing are often not carried out systematically. National and International cement companies operate modern cement kilns which could substitute a part of their fossil fuel and raw material with suitable waste streams to be co-processed. Co-processing non-recyclable waste is often a valid option to close loops towards circular economy. This technology is widely used in different European countries, but with different environmental impacts. Therefore, it is important to investigate the environmental potential of this technology, which is variable for different waste morphology conditions.The potential benefits of the technology of solid waste co-processing in cement kilns are investigated. The methodology of estimation of greenhouse gas emissions for biogenic emissions in determining the benefits and environmental potential of the technology is applied. The example of the Ukrainian cement industry identified the possibility of: reducing the anthracite coal consumption in clinker production up to 262 kt/a; preventing up to 284 ktCO2eq/a emissions from coal substitution. For the waste management sector, the potential of co-processing is identified: MSW disposal up to 1,213 ktMSW/a; prevention of greenhouse gas emissions up to 111 ktCO2eq/a in landfills. These findings are important in a number of countries, as the key barriers to co-processing in cement kilns are related. Environmental analysis results and proposed measures to avoid the identified key barriers to technology implementation can be applied to many countries

Effect of addition of surface water treatment sludge to biomass in biochar porosity

Samples of pruning sawdust (PS) and water treatment plant (WTP) sludge residue were collected and mixed in proportions of 10 to 80% of WTP sludge in PS, submitted to torrefaction at 260 °C, and the resulting biochar samples were submitted to TG/DTG analysis to assess their decomposition, thermal stability, and immediate analysis. Also, the nitrogen adsorption–desorption isotherm, mercury-injection capillary pressure (MICP), ultimate analysis, SEM, EDS, and FTIR were employed. The biochars of blend with 20% of sludge (BB20) and PS without sludge (BBM) were the ones that presented the best stability test in an aqueous medium. The biochar BB20 presented thermal stability (190 °C), moisture (5.7%), volatiles (48.6%), fixed carbon (35.9%), ash (9.8%), BET surface area ($$0.7942\,{\hbox {m}}^{2}{\hbox {g}}^{-1}$$), mean pore diameter ($$389.13\,{\AA}$$), adsorption–desorption isotherm characteristic of the mesoporous material, highest MICP total pore volume, porosity (76.7%), total pore area ($$62.859\,{\hbox {m}}^{2}{\hbox {g}}^{-1}$$), mean pore diameter ($$0.1322\,\upmu\,{\hbox {m}}$$) , the predominance of macropores. The biochar BBM showed BET surface area ($$1.3366\,{\hbox {m}}^{2}\,{\hbox {g}}^{-1}$$), mean pore diameter ($$169.97\,{\AA}$$), adsorption–desorption isotherm characteristic of mesoporous material, better second one MICP total pore volume, porosity (64.4%), total pore area ($$76.520\,{\hbox {m}}^{2}\,{\hbox {g}}$$), mean pore diameter ($$0.0786\,\upmu \hbox {m}$$) also, macroporosity. According to the results presented, the biochar BB20 itself to several uses as substitution of anthracite coal in water and filtration systems plant for the wastewater treatment due to macroporosity and as a viable solution to the reuse of these two residues.

A study of densified biochar as carbon source in the silicon and ferrosilicon production

Biochar pellets were investigated as renewable reducing agents in substitution of coal and coke in the silicon and ferrosilicon production, where a high reactivity, good mechanical properties and low feedstock costs are appreciated. The usage of pyrolysis oil as binder was investigated as way to improve the quality of the pellets. Norway spruce biochar produced at 500, 800 and 1100 °C, was pelletized blended with pyrolysis oil and lignosulphonate. A second heat treatment was carried out at the same temperatures to evaluate the interaction between biochar and pyrolysis oil and to imitate the thermal stability of the pellets when used in a furnace. Density, tensile strength and mechanical durability were analyzed before and after the second heat treatment. The CO2 reactivity was investigated under non-steady conditions. It was observed that the pellet quality is affected by the pyrolysis temperature, showing a relevant difference in properties between 500 °C and 800 °C. The combination of lignosulphonate and pyrolysis oil improved considerably the density and mechanical durability of the pellets. By the second heat treatment, the quality of the pellets was bettered significantly. Densification seems to reduce CO2 reactivity; however, pellets showed a still high reactivity.

Potential impacts of coal substitution policy on regional air pollutants and carbon emission reductions for China's building sector during the 13th Five-Year Plan period

Scattered coal consumption in the building sector contributes approximately 40% of China's primary fine particulate matter emissions and 10% of fossil fuel CO2 emissions, posing serious threats to climate change mitigation and air quality. Therefore, a shift from coal to natural gas (NG) and electricity is of great significance for the synergistic reduction of air pollutants and carbon emissions. However, the lack of building energy statistics at finer spatial scales makes it difficult to form targeted local strategies. In this study, a spatial downscaling framework was developed to project building energy consumption with higher resolution based on openly available information. Then, major air pollutant emission reductions induced by scattered coal substitution policies were estimated from national, provincial and city perspectives. The role played by buildings in realizing the overall carbon mitigation potential was also evaluated. The results show that a policy-driven increase in NG and electricity consumption during the 13th Five-Year Plan (FYP) period could contribute 15% and 4% to national SO2 and NOx emission control targets, respectively, and is helpful for some less-developed areas in achieving greater health benefits and faster low-carbon transformation. Finally, policy recommendations are proposed according to regional differences in emission reduction performance and socioeconomic development.

Reducing coal consumption by people empowerment using local waste processing unit

Until the next following decades, energy mixed in Indonesia will be dominated by coal. Many studies assert that biomass can be used as coal substitution but it is not the case in the real world because the cost of biomass is still higher than the coal price. This study proposes the cheaper way of making biomass by using special method of local waste processing unit that has a patented name, TOSS. This kind of biomass, which was invented by STT PLN Jakarta, school of technology, is more economical than other biomass because waste as raw materials is much cheaper than other commonly used biomass like wooden forestry or agroplantations. Many cities in the world are solving their municipal waste problem by using large scale and high tech approach, which process is conducted in the landfill area. TOSS is using small scale and simple technology that can convert waste to become pellet by local people in its source. The pilot project at Klungkung showed that the pellet of TOSS can be used not only for cooking but also for diesel fuel substitution. This study will use that finding to show that TOSS pellet can also reduce coal consumption by mixing it with normal coal. The simulation is conducted by calculating the equivalent energy and capacity of waste energy from TOSS in term of coal equivalent under the context of Indonesia.

Life cycle assessment (LCA) refuse derived fuel (RDF) waste in pusat inovasi agro teknologi (PIAT) Universitas Gadjah Mada as alternative waste management for energy

Pusat Inovasi Agroteknologi (PIAT) handles institutional waste generated from Universitas Gadjah Mada (UGM). Waste from UGM is called Institutional Solid Waste (ISW) reaches 1,427.27 kg / week. In this study, Life Cycle Assessment (LCA) analysis was used as a tool to calculate and evaluate the environmental impact of potential ISW conversion to densified Refused Derived Fuel (dRDF) with gate to gate framework system. For simulation, OpenLCA software equipped with Ecoinvent database was used in this work. The results showed that conversion of combustible inorganic waste into densified Refuse Derived Fuel (dRDF) along with conversion of organic waste into compost gave following environmental impacts: global warming potential of 1.3E+00 kg CO2 eq, acidification 3.9E-03kg SO4 eq., eutrophication 7.1E-01 kg P eq., human toxicity 1.2E+00 kg 1.4-dichlorobenzene and terrestrial ecotoxicity 6.1E-02 kg 1.4-dichlorobenzene. By separating combustible from non-combustible inorganic waste may significantly improve the quality of dRDF as well as the quantity of compost. The substitution of coal using dRDF combined with the selling of compost is a feasible option. In addition, our results also showed that installation of exhaust gas emission control could further reduce the environmental impact of dRDF production. An economic evaluation was also conducted to evaluate the scenario of converting ISW into dRDF and compost. This option appeared to be profitable, provided that no restrictions to the processed waste, steady flow of dRDF product to the end-users, and the presence of standard price for dRDF.

Reducing emissions of the fast growing Vietnamese coal sector: The chances offered by biomass co-firing

Vietnam's Power Development Plan 7A authorized many new coal power plants projects, implying an increase of greenhouse gases emissions from 90 MtCO2eq/year today to 360 MtCO2eq/year in 2030. How could co-firing technology –that is the partial substitution of coal by biomass– contributes to mitigate that problem? In this study, we assess the costs and potentials of co-firing rice residues in present and planned coal power plants in Vietnam using a spatially explicit optimization model: BeWhere, adapted as recursive annual dynamic. We found that, the cost of CO2 emissions is the key parameter determining at what level the technology is used. A cost of CO2 emissions of 8 $/tCO2 mobilizes the maximum technical potential of the rice straw and husk domestic resource, with an annual emission reduction of 28 MtCO2eq/year by 2030. At this level, biomass co-firing contributes to an 8% emission reduction in the coal power sector with the abatement cost of 137 Million USD.

Potential impact of shifting coal to gas and electricity for building sectors in 28 major northern cities of China

Building sector accounts for about 30% of total primary energy consumption in Chinese cities, in which the untreated scattered coal is one of the most important sources for local air pollutants such as SO2, NOx, PM2.5 and carbon emissions, posing serious threats on air quality, public health and climate change. This work aims to evaluate the impacts of the coal substitution policy (“coal-to-gas” and “coal-to-electricity”) on building energy demand and emissions for Beijing, Tianjin, and other twenty-six cities along the “air pollution transmission channel”, which has not been fully studied before and could assist city policy makers in coping with this drastic energy transformation by weighing potential social costs and benefits. To this end, a systematic method to downscale building energy consumption from provincial/regional level to grid level (0.1° × 0.1°) is developed using openly available data and information to establish high resolution emission projections of CO2 and major air pollutants (SO2, NOx and PM2.5) for these cities. This framework provides a convenient way to simulate the spatiotemporal dynamics of future emissions by sector for multiple cities. Combined with three coal substitution scenarios designed in this study, some policy suggestions on alternative energy and social welfare improvement were made by investigating city scale effects on energy accessibility, affordability, as well as health and environmental benefits.

Ignition sensitivity of different compositional wood pellets and particle size dependence

Partial or complete substitution of coal with renewable biomass like wood is a sustainable and effective solution to reduce the CO2 emissions in the atmosphere. Utilization of these woods in the form of compact pellets facilitates in its handling and transportation with higher energy density. However, for electric power generation the pellets are broken up into their constituent milled finer particles for burning as a pulverised biomass flame. There is a dust fire/explosibility hazards in the process handling facilities such as in storage, conveying and milling. In the present work, four commercial pellets were investigated, and each pellet sample was split into three size ranges <63 μm, 63–500 μm and <500 μm. The flame propagation characteristics and their lean flammability limit for each pulverised pellet was determined using modified Hartmann dust explosion tube. It was found that the fine particles, with lower lean flammability limits of 0.3–0.7 equivalence ratio, intensify the explosibility risk (dP/dt of 10–15 bar/s for most reactive concentration) of the dust due to fast volatile release rate. Comparison was also made between particle size distribution (PSD) of the finer fractions (<63 μm) of wood samples in comparison to crop residue samples that showed 70–80% larger size distribution for wood samples due to elongated particles as showed by Scanning Electron Microscope (SEM). Results showed that the ash + moisture content had a stronger effect on wood samples than on agricultural residue's samples. The results showed that the explosibility characteristics of the pellets industry's feed-stocks was variable and dependent on the pellet composition and this needs to be taken into account in explosion protection and in utilising the pellets in the main pulverised biomass combustion.

Municipal Solid Waste (MSW) characterization for possible Waste-to-Energy (WtE) conversion in Zambia

Coal has traditionally been relied upon as a good source of bulk energy in many pyro processes especially in cement manufacturing and thermal power generation. In Zambia, cement manufacturing, a key and growing industry, uses coal as the main source of energy for the pyro process in the cement kiln that converts raw materials to a semi-finished product called clinker. Despite the advantages that coal has over other sources of energy in this market including its high energy content and its easy accessibility, burning coal has significant known and documented disadvantages especially towards the environment and human health that give way to dissenting views on its continued use. In attempts to address the environmental effects of coal usage in cement manufacturing and consequently contribute to the lowering of production costs, Cement manufacturing companies have been pursuing the possibilities of coal substitution with Municipal Solid Waste (MSW). The MSW should however; conform to certain standards before it can be used in the substitution in order not to affect the quality of cement produced. This paper sought to characterize the Municipal Solid Waste in Lusaka to ascertain its conformity to internationally recognized standards in order to be used in coal substitution. The results show that the characterization of MSW showed that it could be a viable substitute for coal burning in cement manufacturing in Zambia. Apart from the high moisture content in the rainy season, the other readings were all favorable to its use as an alternate energy source. The high moisture content meant that during the pre-treatment for possible use in the cement manufacturing, pretreatment processes could be employed to help align the moisture content before its use as the substitute for coal in cement manufacturing.

A comparative analysis of substituting imported gas and coal for electricity with renewables – An input-output simulation

For many countries, the leading energy system decarbonisation strategy is to decrease reliance on imported fossil-fuel by developing renewable electricity. This paper offers insights on the net effects of transition to low fossil-based electricity by adapting an input-output (I-O) substitution model. Firstly, it addresses a common challenge with national I-O tables, namely how to isolate figures for inhomogeneous products like ‘electricity’ and ‘gas’ aggregated into one sector for a case study of Ireland. Secondly, it applies an extended I-O model to compare the net impacts on energy and non-energy sectors when substituting imported fossil fuels for electricity with renewable resources. Within the framework of the I-O model, for each 1% GHG reduction of the gas substitution scenario, there are increases of 26.2 net jobs and €5.1 m net value-added. These impacts are lower by 73–78% for coal substitution scenarios. Without taking account of the lost jobs and value-added from the economy, the job creations and value-added of renewable electricity would be overestimated by 17%–35% and 25%–50%, respectively. As well as giving insights into the net benefits of renewable electricity, the study provides techniques that could be applied to I-O tables for other jurisdictions to enable improved analysis of energy scenarios.

Biomass pellets for power generation in India: a techno-economic evaluation

Modern bioenergy is being recognized as an increasingly important low-carbon resource by policy-makers around the world to meet climate policy targets. In India also, there is a clear recognition of the significant role of bioenergy in electricity generation as well as in other applications. In this study, a preliminary attempt has been made to assess the techno-economic feasibility of biomass pellets-based power (BPBP) generation in India. Surplus availability of biomass feedstock from agriculture and forestry/wasteland sector is estimated at 242 million tonnes (Mt) for 2010–11 and is expected to rise to 281 Mt in 2030–31 due to increased crop production and associated waste/residue availability. In terms of related capacity, the potential of BPBP projects is estimated at 35 GW for 2030–31. The associated carbon dioxide mitigation potential resulting from the substitution of coal is estimated at 205 Mt in 2030–31 if the entire biomass surplus is to be diverted for power generation. The levelized cost of electricity is estimated at €0.12 per kWh for BPBP projects as compared to €0.10 per kWh for imported coal based power plants. For states with the lower tariff for biomass power, the break-even price of carbon for BPBP projects is estimated at €18 per tonne. Additionally, BPBP projects will generate employment of more than 5 million person-months in the construction of biomass power plants and over 200,000 full-time employments in the operation of BPBP plants and in the production of biomass pellets.

Lignocellulose thermal pretreatment and its effect on fuel properties and composition of the condensable products (tar precursors) from char devolatilization for coal substitution in gasification application

To establish the potential of thermally pretreated biomass as fuel for coal replacement in applications such as gasification, the fuel properties (higher heating value, elemental and proximate analyses) and the composition of char devolatilization products were analyzed and compared to those of sub-bituminous coal. Samples of pine, bamboo, corn cob and corn stover were pretreated at 250, 300, 350 and 400 °C with a hold time of 30 min. The devolatilization experiments were done in a Thermogravimetric analyzer, while captured volatiles were analyzed by thermal desorption/gas chromatography–mass spectrometry. The results showed that an increase in pretreatment temperature consistently decreased the oxygen and volatile matter contents of the char, while its fixed carbon content and the higher heating values increased, with a more drastic evolution from 300 °C onwards. Analysis of the char devolatilization products confirmed a major modification of the polysaccharides structure, as only traces of depolymerisation products were observed following pretreatment at 350 °C. Devolatilization of chars pretreated at 350 and 400 °C resulted in the evolution of the tar precursors, especially the phenolics, at similar and lower amounts, respectively, in comparison to coal devolatilization. Overall, a pretreatment temperature of at least 350 °C would be recommended for sub-bituminous coal substitution in gasification, while 400 °C could be considered for biomass species with high lignin content.

Leaching behavior of fly ash from co-firing of coal with alternative off gas fuel in powerplant boilers

The attenuation of climate changes through substitution of coal with GHG-neutral or low-emission fuels, a replacement of non-renewable resources with renewable ones and reuse of waste materials is being achieved among others by partial or total substitution of coal in power plants with alternative fuels that may affect the composition and leaching behavior of coal fly ash (CFA), and therefore its environmental impact in disposal/reuse sites. A comparison of the most widespread primary alkaline Class F CFA of Sialic type from coal combustion with fly ash from co-combustion of the same coal with process off gas in powerplant boilers (CGFA – coal/gas fly ash) revealed certain reduction of pH, CaO, MgO and Fe2O3, and simultaneous increase of other major and minor constituents, but in particular of almost all trace element contents (by 35% - 2-fold). However, comparative tests of the leaching behavior of both materials as a function of L/S (Liquid/Solid ratio) and extract pH with the use of recently developed US EPA, SW-846 Methods 1316 and 1313 (2012) showed that the mobility of both major and trace elements in both residuals (apart from their properties as cations, oxyanions and amphoteric species) was governed by several factors, among them availability and equilibria constraints, and followed predominantly a similar pattern. Liquid-solid partitioning as a function of L/S showed higher release of Ca, OH, As, Ba, Br, I, Co, Ni, Sb, Pb and W from CFA, and of Al, Na, K, SO4, Si, B, Cd, Cr, Hg, Li, Mo, Ti and V from CGFA, Se and Sr showed similar leachability, while Ag, Be, Cu, Fe, Mg, Mn, Tl, Zn, Zr were equally immobile. The decisive factor in element release from CFA and CGFA as a function of pH was the pattern of acid/base neutralization capacity (ANC/BNC) of both materials that in CFA and CGFA appeared to be basically different. Due to the gradual reduction of ANC in CGFA opposite to its sharp depletion in CFA, the majority of elements unstable at acidic pH (Ag, Al, As, Ba, Be, Cd, Cu, Fe, Mn, Ni, Pb, Sb, Si, Ti, Tl, V, W, Zn, Zr) were less susceptible to mobilization from CGFA than from CFA. Along with the lower mobility of a number of elements in the entire (Ca, Mg, Cl, Br, Cr), or neutral/acidic (Fe, Mn, Ni, Sb, PO4), or alkaline range (I, Se, CO3), and similar release of K, SO4, Co and Hg, at less developed active surface and interconnected micro-porosity, this makes CGFA from process off gas co-combustion environmentally safer than CFA.

Substitution of coal power plants with renewable energy sources – Shift of the power demand and energy storage

Because of their Global Climate Change contributions, it is desirable to reduce the amount of the global CO2 emissions. One of the ways to accomplish this is the substitution of coal with renewable energy sources, most notably wind and solar. However, the availability of wind energy and of insolation does not follow the diurnal and annual demand patterns of electric power. The large-scale substitution of coal with wind and solar significantly shifts the demand for the rest of the power producing units. When the contribution of wind and solar exceeds approximately 25% of the total annual energy produced, there are time periods within a year when excess electricity is produced that must be wasted/dissipated. This presents a severe constraint for the substitution of coal-generated electricity with renewables. At such production levels diurnal or seasonal storage of energy becomes necessary and hydrogen storage offers the best alternative. Based on the hourly, electricity demand of a region in North Texas, which has very high availability of wind and solar energy and is considered prime region for renewables, extensive calculations are made for: (a) the solar and wind rated power that are necessary for the substitution of part or all the power currently supplied by a coal-fired power plant; and (b) the storage requirements for this substitution. Significant seasonal and diurnal energy storage, on the order of 250,000 m3, is required for the total substitution of coal in the region. The calculations also reveal that the substitution of coal with the renewable energy sources may be optimized for minimum energy storage capacity.