Thermoeconomic analysis of a power/water cogeneration plant

Cogeneration plants for simultaneous production of water and electricity are widely used in the Arabian Gulf region. They have proven to be more thermodynamically efficient and economically feasible than single purpose power generation and water production plants. Yet, there is no standard or universally applied methodology for determining unit cost of electric power generation and desalinated water production by dual purpose plants.A comprehensive literature survey to critically assess and evaluate different methods for cost application in power/water cogeneration plants is reported in this paper. Based on this analysis, an in-depth thermoeconomic study is carried out on a selected power/water cogeneration plant that employs a regenerative Rankine cycle. The system incorporates a boiler, back pressure turbine (supplying steam to two MSF distillers), a deaerator and two feed water heaters. The turbine generation is rated at 118 MW, while MSF distiller is rated at 7.7 MIGD at a top brine temperature of 105 °C. An appropriate costing procedure based on the available energy accounting method which divides benefits of the cogeneration configuration equitably between electricity generation and water production is used to determine the unit costs of electricity and water. Capital charges of common equipment such as the boiler, deaerator and feed water heaters as well as boiler fuel costs are distributed between power generated and desalinated water according to available energy consumption of the major subsystems. A detailed sensitivity analysis was performed to examine the impact of the variation of fuel cost, load and availability factors in addition to capital recovery factor on electricity and water production costs.     

A novel polygeneration system integrating the acetylene production process and fuel cell

This paper presents a novel polygeneration system that integrates the acetylene process and the use of fuel cells. The system produces acetylene and power by a process of the partial oxidation/combustion (POC) of natural gas process, a water–gas shift reactor, a fuel cell and a waste heat boiler auxiliary system to recover the exhaust heat and gas from the fuel cell. Based on 584.3 kg/h of natural gas feedstock, a POC reactor temperature of 1773 K, an absorber pressure of 1.013 MPa and a degasser pressure of 0.103 MPa, the simulation results show that the new system achieved acetylene production of 1.9 MW, net electricity production of 1.7 MW, power generation efficiency of 26.8% and exergy efficiency of 43.4%, which was 20.2% higher than the traditional acetylene production process. The new system's exergy analysis and the flow rate of the products were investigated, and the results revealed that the energy conversion and systematic integration mechanism demonstrated the improvement of natural gas energy conversion efficiency.     

Calculation of bright roof-tops for solar PV applications in Dhaka Megacity,Bangladesh

Bangladesh has already been known as the country of power crisis. Although the country's electricity generation capacity is 4275 MW, around 3000–3500 MW of electricity can be generated against the demand of more than 5000 MW. The country's power is being generated mostly with conventional fuel (82% indigenous natural gas, 9% imported oil, 5% coal) and renewable sources (4% hydropower and solar). But recently a remarkable decline of the indigenous gas takes place, which rapidly aggravates electricity generation. Dhaka, the capital as well as prime city of the country with its nearly 14 million populations faces the worst situation due to the shortfall of electricity. Around 1000–1200 MW of electricity is supplied to Dhaka Megacity, while the existing demand is nearly 2000 MW. As a result frequent load shedding takes place and most of the service sectors in the city are interrupted, which has recently created immense dissatisfaction among the city-dwellers. Given the city's power crisis and geophysical situations, applications of either stand-alone or grid connected PV systems would be very effective and pragmatic for power supplement. The conservative calculation of bright roof-tops from the Quickbird Scene 2006 of Dhaka city indicates that the city offers 10.554 km² of bright roof-tops within the Dhaka City Corporation (DCC) ward area (134.282 km²). The application of stand-alone PV systems with 75 Wp solar modules can generate nearly 1000 MW of electrical power, which can substantially meet the city's power demand.     

Assessment of the renewable energies potential for intensive electricity production in the province of Jaén,southern Spain

The foreseen depletion of the traditional fossil fuels for the forthcoming decades is forcing us to seek for new sustainable and non-pollutant energy sources. Renewable energies rely on a decentralized scheme strongly dependent on the local resources availability. In this work, we tackle the study of the renewable energies potential for an intensive electricity production in the province of Jaén (southern Spain) which has a pronounced unbalance between its inner electricity production and consumption. The potential of biomass from olive pruning residues, solar photovoltaics (PV) and wind power has been analyzed using Geographical Information System tools, and a proposal for a massive implementation of renewable energies has been arisen. In particular, we propose the installation of 5 biomass facilities, totaling 98 MW of power capacity, with an estimated annual production of 763 GWh, 12 PV facilities, totaling 420 MW of power capacity, with an estimated annual production of 656 GWh and 506 MW of wind power capacity in a number of wind farms, with an estimated annual production of 825 GWh. Overall, this production frame would meet roughly a 75% of the electricity demands in the province and thus would mitigate the current unbalance.     

Future of renewable energies in Iran

The activities in field of renewable energy in Iran are focused on scientific and research aspects, and research part is aimed at reduction of capital required for exploitation of related resources. The second step is to work research results into scientific dimension of this field for practical means, i.e. establishing electricity power plants. Due to recent advancements in wind energy, many investors in the country have become interested in investing in this type of energy. At the moment, projects assuming 130 MW of wind power plants are underway, of which, 25 MW is operational. Based on the planning in the 4th Socioeconomic and Cultural Development Plan (2005–2010), private sector is expected to have a share of at least 270 MW in renewable energies. However, it is the government's duty to take the first step for investment in biomass and solar power plants; private sector may then play its part once the infrastructures to this end are laid out. At the moment, a 250 kW plant is under construction in Shiraz and two more geothermal units with 5 and 50 MW capacities will follow. Moreover, two biomass and solar energy plants, standing at 10 and 17 MW, respectively, are of other upcoming projects. The project of Iran's renewable energy, aims to accelerate the sustainable development of wind energy through investment and removal of barriers. This preparatory project is funded by the global environment facility (GEF) and will provide for a number of international and national consultant missions and studies. Once the studies are concluded, a project to develop 25 MW of wind energy in the Manjil region of Gilan will be prepared. It will be consistent with the national development frameworks and objectives and form part of 100 MW of wind-powered energy, which is expected to be developed under the government's third 5-year national development plan (started 21 March 2000).     

Integration of Kalina cycle in a combined heat and power plant,a case study

This paper presents the integration of the Kalina cycle process in a combined heat and power plant for improvement of efficiency. In combined heat and power plants, the heat of flue gases is often available at low temperatures. This low-grade waste heat cannot be used for steam production and therefore power generation by a conventional steam cycle. Moreover, the steam supply for the purpose of heating is mostly exhausted, and therefore the waste heat at a low-grade temperature is not usable for heating. If other measures to increase the efficiency of a power plant process, like feed-water heating or combustion air heating, have been exhausted, alternative ways to generate electricity like the Kalina cycle process offer an interesting option. This process maximizes the generated electricity with recovery of heat and without demand of additional fuels by integration in existing plants. The calculations show that the net efficiency of an integrated Kalina plant is between 12.3% and 17.1% depending on the cooling water temperature and the ammonia content in the basic solution. The gross electricity power is between 320 and 440 kW for 2.3 MW of heat input to the process. The gross efficiency is between 13.5% and 18.8%.     

The role of energy storage in accessing remote wind resources in the Midwest

Replacing current generation with wind energy would help reduce the emissions associated with fossil fuel electricity generation. However, integrating wind into the electricity grid is not without cost. Wind power output is highly variable and average capacity factors from wind farms are often much lower than conventional generators. Further, the best wind resources with highest capacity factors are often located far away from load centers and accessing them therefore requires transmission investments. Energy storage capacity could be an alternative to some of the required transmission investment, thereby reducing capital costs for accessing remote wind farms. This work focuses on the trade-offs between energy storage and transmission. In a case study of a 200 MW wind farm in North Dakota to deliver power to Illinois, we estimate the size of transmission and energy storage capacity that yields the lowest average cost of generating and delivering electricity ($/MW h) from this farm. We find that transmission costs must be at least $600/MW-km and energy storage must cost at most $100/kW h in order for this application of energy storage to be economical.     

Full-scale co-firing trial tests of sawdust and bio-waste in pulverized coal-fired 230 t/h steam boiler

Co-firing trial tests of sawdust and bio-waste coming from cereal production with hard coal were carried out at Skawina Power Plant in Poland (1532 MW in fuel, currently belonging to CEZ Group). Skawina Power Plant is a tangentially-fired pulverized coal unit with nine boilers (4 boilers of 210 t/h and five boilers of 230 t/h live steam respectively) that produces 590 MW electricity and 618 MW of heat (district heating and process steam).The paper presents an analysis of energy and ecological effects of sawdust and bio-waste co-firing in the existing pulverized hard coal boiler. The mixture of coal and biomass was blended in the coal yard, and fed into the boiler through the coal mills. During the tests, combustion of mixtures composed of hard coal and sawdust (with mass share of 9.5%) and hard coal – bio-waste (6.6% mass basis) were examined. The co-firing tests were successful. Based on the analysis of the test results, the influence of biomass co-firing on specific components of energy balance (e.g. stack losses and boiler thermal efficiency) was discussed, in comparison to combustion of coal alone. The emission indices during coal combustion were calculated and compared to the emission indices for biomass co-firing. It was proved that co-firing of both biomass sorts leads to a decrease of CO and SO₂ emissions. Due to the possibility of considering the part of the energy generated during biomass co-firing as renewable energy, the procedure for biomass based renewable energy share determination is presented and illustrated with an example.     

A probabilistic method for calculating the usefulness of a store with finite energy capacity for smoothing electricity generation from wind and solar power

This paper describes a novel method of modelling an energy store used to match the power output from a wind turbine and a solar PV array to a varying electrical load. The model estimates the fraction of time that an energy store spends full or empty. It can also estimate the power curtailed when the store is full and the unsatisfied demand when the store is empty. The new modelling method has been validated against time–stepping methods and shows generally good agreement over a wide range of store power ratings, store efficiencies, wind turbine capacities and solar PV capacities.Example results are presented for a system with 1 MW of wind power capacity, 2 MW of photovoltaic capacity, an energy store of 75% efficiency and a range of loads from 0 to 3 MW average.     

Assessing the economic wind power potential in Austria

In the European Union, electricity production from wind energy is projected to increase by approximately 16% until 2020. The Austrian energy plan aims at increasing the currently installed wind power capacity from approximately 1 GW to 3 GW until 2020 including an additional capacity of 700 MW until 2015. The aim of this analysis is to assess economically viable wind turbine sites under current feed-in tariffs considering constraints imposed by infrastructure, the natural environment and ecological preservation zones in Austria. We analyze whether the policy target of installing an additional wind power capacity of 700 MW until 2015 is attainable under current legislation and developed a GIS based decision system for wind turbine site selection.Results show that the current feed-in tariff of 9.7 ct kW h⁻¹ may trigger an additional installation of 3544 MW. The current feed-in tariff can therefore be considered too high as wind power deployment would exceed the target by far. Our results indicate that the targets may be attained more cost-effectively by applying a lower feed-in tariff of 9.1 ct kW h⁻¹. Thus, windfall profits at favorable sites and deadweight losses of policy intervention can be minimized while still guaranteeing the deployment of additional wind power capacities.     

Cogeneration potential in the Columbian palm oil industry: Three case studies

The palm oil mills are characterized by the availability of considerable amounts of by-products of high-energy value such as empty fruit bunches (EFB), fibers, shells and liquid effluents with high content of organics called palm oil mill effluent (POME). A palm oil mill produces residues equivalent to almost three times the amount of oil produced by biomass, showing a huge potential for increasing the power efficiency of the plants and installed power, mainly by the use of by-products in cogeneration plants with high steam parameters and by reducing steam consumption in process. The objective of this paper is to present the results of the study about the cogeneration potential for three representative palm oil mills located in two important palm oil producing regions in Colombia (South-America), fifth palm oil producers of the world. The sizing of the cogeneration system was made assuming it operation during the greatest possible number of hours throughout the year (based on the seasonal availability of fruit) considering parameters for the steam at 2 MPa and 350 °C, using a condensing-extraction turbine. The balance of mass and energy was made by using the Gate Cycle Enter Software, version 5.51, to estimate the potential of electricity generation. The results showed that for fresh fruit bunch (FFB) processing capacities between 18 and 60 t FFB h⁻¹, it is possible to have surplus power ranging between 1 and 7 MW, if the plants are self-sufficient in electric energy and steam for process. With an average Capacity Factor (approximately 0.4), it is possible to expect a generation index of 75 and 160 kWh t⁻¹ FFB when the processing plant is operating or shutdown, respectively, 3 or 4 times better than when a traditional system with a back-pressure steam turbines is used. This analysis used up to 60% of EFB produced in plant as fuel, considering its value as fertilizer for the palm crop. Several economic conditions were considered to estimate the economic and technical feasibility of cogeneration systems in palm oil mill for Colombian palm oil sector.     

Biomass and central receiver system (CRS) hybridization: Volumetric air CRS and integration of a biomass waste direct burning boiler on steam cycle

Concentrated solar power (CSP) plants generate an almost continuous flow of fully dispatchable “renewable” electricity and can replace the present fossil fuel power plants for base load electricity generation. Nevertheless, actual CSP plants have moderate electricity costs, in most cases quite low capacity factors and transient problems due to high inertia. Hybridization can help solve these problems and, if done with the integration of forest waste biomass, the “renewable” goal can be maintained, with positive impact on forest fire reduction. Local conditions, resources and feed in tariffs have great impact on the economical and technical evaluation of hybrid solutions; one of the premium European locations for this type of power plants is the Portuguese Algarve region.Due to the concept innovation level, conservative approaches were considered to be the best solutions. In this perspective, for a lower capital investment 4 MWe power plant scale, the best technical/economical solution is the hybrid CRS/biomass power plant HVIB3S4s with CS3 control strategy. It results in a levelized electricity cost (LEC) of 0.146 €/kWh, with higher efficiency and capacity factor than a conventional 4 MWe CRS. A larger 10 MWe hybrid power plant HVIB3S10s could generate electricity with positive economical indicators (LEC of 0.108 €/kWh and IRR of 11.0%), with twice the annual efficiency (feedstock to electricity) and lower costs than a conventional 4 MWe CRS. It would also lead to a 17% reduction in biomass consumption (approximately 12,000 tons less per year) when compared with a typical 10 MWe biomass power plant – FRB10; this would be significant in the case of continuous biomass price increase.     

Wind energy status in renewable electrical energy production in Turkey

Main electrical energy sources of Turkey are thermal and hydraulic. Most of the thermal sources are derived from natural gas. Turkey imports natural gas; therefore, decreasing usage of natural gas is very important for both economical and environmental aspects. Because of disadvantages of fossil fuels, renewable energy sources are getting importance for sustainable energy development and environmental protection. Among the renewable sources, Turkey has very high wind energy potential. The estimated wind power capacity of Turkey is about 83,000 MW while only 10,000 MW of it seems to be economically feasible to use. Start 2009, the total installed wind power capacity of Turkey was only 4.3% of its total economical wind power potential (433 MW). However, the strong development of wind energy in Turkey is expected to continue in the coming years. In this study, Turkey's installed electric power capacity, electric energy production is investigated and also Turkey current wind energy status is examined.     

An ex-post analysis of the effect of renewables and cogeneration on Spanish electricity prices

Growing concerns about climate change and energy dependence are driving specific policies to support renewable or more efficient energy sources such as cogeneration in many regions, particularly in the production of electricity. These policies have a non-negligible cost, and therefore a careful assessment of their impacts seems necessary. In particular, one of the most-debated impacts is their effect on electricity prices, for which there have been some ex-ante studies, but few ex-post studies. This article presents a full ex-post empirical analysis, by looking at use of technologies and hourly electricity prices for 2005–2009 in Spain, to study the effects that the introduction of renewable electricity and cogeneration has had on wholesale electricity prices. It is particularly interesting to perform this study in Spain where an active system of public support to renewables and cogeneration has led to a considerable expansion of these energy sources and electricity pricing is at the center of intense debate. The paper reports that a marginal increase of 1 GWh of electricity production using renewables and cogeneration is associated with a reduction of almost 2 € per MWh in electricity prices (around 4% of the average price for the analyzed period).     

Solar electricity in a changing environment: The case of Spain

In Spain, solar electricity (photovoltaic and thermoelectric) has reached a stable annual capacity factor above 20% since 2009; while wind achieved 23% since more than 10 years ago. This is the demonstration of an ongoing transition towards a more sustainable energy mix, further corroborated by the reduction of the capacity factor of gas-fired technology, which has seen a decline to values lower than 10% after an initial promising rise; this is a very low value for a fossil-fuel technology. Additionally, hydro installed capacity, which has been stable for the past 20 years, have demonstrated that can be used as a back-up power source in combination with solar and wind electricity, and it is capable of producing energy peaks that may increase from a stable base of 2000 GWh/month up to 6000 GWh/month and therefore meet demand at some particular times when solar and wind are generating less electricity without the need of installing new additional capacity at national level.     

Wind energy as a potential generation source at Ras Benas,Egypt

Analysis of the wind characteristics in Ras Benas city located on the east coast of Red Sea in Egypt using measured data (wind, pressure and temperature) and Weibull function were made.Statistical analysis model to evaluate the wind energy potential was introduced. According to the power calculations done for the site, the annual mean wind density is 315 kW/m² at a height of 70 m above ground level. This station has a huge wind energy potential for electricity generation, especially during spring and summer seasons, comparing with some European countries.In addition, the monthly wind turbine efficiency parameter (η_monthly) has been calculated by using a commercial wind turbine 1 MW with 70 m hub height to help designers and users in evaluating the potentialities and choosing the suitable wind turbine for the considered site. The use of wind turbine with capacity greater than 1000 kW at this station was recommended.Ras Benas station was selected to install 30 MW-wind farm consists of 20 commercial wind turbines (Nordex S 77) with hub heights and Rotor diameter were 100 and 77 m, respectively. This site has annual wind speed more than 9.8 m/s at 100 m height and enough area to locate these turbines.The estimated energy production using WASP Program of these wind farm was 130 GWh/year. Furthermore, the production costs was found 1.3€ cent/kWh, which is a competition price at the wind energy world market.     

Contribution of renewable energy sources to electricity production in the La Rioja Autonomous Community,Spain. A review

The implementation of the emissions market should imbue renewable energies with a greater degree of competitiveness regarding conventional generation. In order to comply with the Kyoto protocol, utilities are going to begin to factor in the cost of CO₂ (environmental costs) in their overall generating costs, whereby there will be an increase in the marginal prices of the electricity pool.This article reviews the progress made in the La Rioja Autonomous Community (LRAC) in terms of the introduction of renewable energy technologies since 1996, where renewable energy represents approximately only 10% of the final energy consumption of the LRAC. Nonetheless, the expected exploitation of renewable energies and the recent implementation of a combined cycle facility mean that the electricity scenario in La Rioja will undergo spectacular change over the coming years: we examine the possibility of meeting a target of practical electrical self-sufficiency by 2010.In 2004, power consumption amounted to 1494 GWh, with an installed power of 1029.0 MW of electricity. By 2010, the Arrúbal combined cycle facility will produce around 9600 GWh/year, thereby providing a power generation output in La Rioja of close to 2044.7 MW, which will involve almost doubling the present output, and multiplying by 8.9 that recorded in this Autonomous Community in 2001.     

Investigation of coal-fired power plants in Turkey and a case study: Can plant

About 61% of the total installed capacity for electrical power generation in Turkey is provided by thermal resources, while 80% of the total electricity is generated from thermal power plants. Of the total thermal generation, natural gas accounts for 49.2%, followed by coal for 40.65%, and 9.9% for liquid fuel. This study deals with investigation of the Turkish coal-fired power plants, examination of an example plant and rehabilitation of the current plants. Studied plant has a total installed capacity of 2 × 160 MW and has been recently put into operation. It is the first and only circulating fluidized bed power plant in the country. Exergy efficiencies, irreversibilities, and improvement factors of turbine, steam generator and pumps are calculated for plant selected. Comparison between conventional and fluidized bed power plant is made and proposed improving techniques are also given for conventional plants.     

Exergetic and thermoeconomic analyses of diesel engine powered cogeneration: Part 2 – Application

This paper is Part 2 of the study on the exergetic and thermoeconomic analysis of diesel engine powered cogeneration (DEPC) systems. In Part 1, formulations and procedure for such a comprehensive analysis are provided while this paper provides an application of the developed formulation that considers an actual DEPC plant installed in Gaziantep, Turkey. The plant has a total installed electricity and steam generation capacities of 25.3 MW and 8.1 tons/h at 170 °C, respectively. Exergy destructions, exergy efficiencies, exergetic cost allocations, and various exergoeconomic performance parameters are determined for the entire plant and its components. The exergy efficiency of the plant is determined to be 40.6%. The exergoeconomic analysis is based on specific cost method (SPECO) and it is determined that the specific unit exergetic cost of the power produced by the plant is 10.3 $/GJ.     

Economic feasibility of large community feed-in tariff-eligible wind energy production in Nova Scotia

Nova Scotia, Canada's community feed-in tariff (COMFIT) scheme is the world's first feed-in tariff program specifically targeting locally-based renewable energy projects. This study investigated selected turbine capacities to optimize electricity production, based on actual wind profiles for three sites in Nova Scotia, Canada (i.e., Sydney, Caribou Point, and Greenwood). The turbine capacities evaluated are also eligible under the current COMFIT-large scheme in Nova Scotia, including 100 kW, 900 kW and 2.0 MW turbines. A capital budgeting model was developed and then used to evaluate investment decisions on wind power production. Wind duration curves suggest that Caribou Point had the highest average wind speeds but for shorter durations. By comparison, Sydney and Greenwood had lower average wind speeds but with longer durations. Electricity production cost was lowest for the 2.0 MW turbine in Caribou Point ($0.07 per kWh), and highest for the 100 kW turbine located in Greenwood ($0.49 per kWh). The most financially viable wind power project was the 2.0 MW turbine assumed to operate at 80 m hub height in Caribou Point, with NPV=$251,586, and BCR=1.51. Wind power production for the remaining two sites was generally not financially feasible for the turbine capacities considered. The impact of promoting local economic development from wind power projects was higher in a scenario under which wind turbines were clustered at a single site with the highest wind resources than generating a similar level of electricity by distributing the wind turbines across multiple locations.