A thermodynamic platform for evaluating the energy efficiency of combined power generation and desalination plants

Both brackish water desalination and seawater desalination processes are well established and in common use around the globe to create new water supply sources. The farther the location of the source water from the ocean or seashore, the lower the salinity (TDS) of the water and the lower the osmotic pressure that needs to be overcome when desalinated water is produced. This is one of the major reasons that brackish desalination is often considered less costly than seawater desalination. A number of project considerations, however, indicate that seawater desalination can be beneficial and more cost-effective than brackish water desalination. To make a fair comparison, we need to properly compare all major aspects of both types of projects to define the best and most appropriate desalination technology. While brackish water has less feed water TDS, it is more challenging to dispose of the produced concentrate. Also, although brackish water desalination needs less energy to overcome osmotic pressure, it usually requires more energy to draw the water from the well than it takes to pump seawater from the open ocean intake. Another factor is that the temperature of the brackish well water may be lower than the temperature of ocean water, giving seawater desalination an advantage in energy demand. In comparing brackish to seawater desalination, these major aspects should be evaluated: (1) Locations of seawater and brackish water plants, relative to the major consumers of the desalinated water, (2) Transportation (pumping and disposal) costs of the feed water and produced water, (3) Potential colocation of a seawater plant with a large industrial user (e.g., power plant) of the seawater for cooling or other purposes, (4) Produced quality of brackish water and seawater desalination in terms of major minerals and emerging contaminants, (5) Sustainability of the water source: capacity and depth of the brackish water wells, as well as the type of soil. (6) Technical and economic aspects of produced concentrate disposal, (7) Permitting process costs for brackish and seawater desalination, and (8) The economics of both brackish and seawater desalination treatment processes: capital costs, operational and maintenance (O&M) costs, lifetime water cost, and total water cost (TWC). This paper discusses the major evaluation criteria and considerations involved in properly comparing the economic and technical aspects of brackish and seawater desalination to determine the more favorable desalination technology for a given desalination project.

Hybrid systems in seawater desalination-practical design aspects, status and development perspectives

Thermodynamic optimization of power plants based on supercritical (SupC) and ultrasupercritical (USC) steam parameters is reported in this article. The objective is to compute the maximum attainable power plant efficiency in Indian climatic conditions using high ash (HA) indigenous coal. A unit size of 800 MWe presently under development in India is considered for energy and exergy analysis of power plants. Commercially established steam turbine parameters are used for the optimization of SupC power plant, whereas advanced steam turbine parameters currently under research and development are used for the optimization of USC power plant. The plant energy efficiency of the optimized SupC and USC power plant based on air-coal combustion (ACC) show considerable increases of 2.8 and 5.2% points, respectively compared with the current SupC ACC power plant (reference plant) being commissioned in India. The increases in plant exergy efficiency for the same power plants are 2.6 and 4.8% points and the corresponding CO2 reductions are about 6 and 11%, respectively. The maximum possible plant energy efficiency in Indian climatic conditions using HA Indian coal is about 42.7% (USC power plant). The effect of low ash coal on plant energy and exergy efficiencies compared with HA coal is also presented. Further, the effect of oxy-coal combustion (OCC) on the plant energy and exergy efficiencies compared with the ACC is studied for the double reheat SupC and USC power plants to account for the impact of CO2 capture. A significant reduction of 8.8 and 6.6% points in plant energy efficiency is observed for SupC and USC OCC power plants, respectively compared with the reference SupC ACC power plant.

Author Correction: A thermodynamic platform for evaluating the energy efficiency of combined power generation and desalination plants

Analysis and optimization of LT-MED system powered by an innovative CSP plant

Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

The integration of desalination plants and mineral production

The urgency of the work is due to the feasibility of increasing the energy efficiency of solar power plants through the use of solar energy concentrators. Ways to improve the energy efficiency of solar panels using a sys-tem of directional mirrors, flat Fresnel lenses, spherical concentrators and trackers have been investigated. It is established that the most optimal way to improve the energy efficiency of solar panels is to use inexpensive track-ers with a simple design. The analysis of known types of solar panels, which differ in materials from which their elements are made, and the coefficients of efficiency – dependence of energy produced by a photocell on the intensity of solar radiation per unit of its surface has been carried out, and the type of solar panels by the criterion “price-quality” has been selected. A tracker design has been developed to track the angle of inclination of solar panels to increase efficiency. The electricity generated by the proposed solar power plant was calculated using an online calculator. It is projected to reduce losses when generating electricity for a given power plant due to the use of a tracker compared to a fixed power system, with the same number of solar panels. In order to reduce the cost of the tracker, it is suggested to orientate it to the south at once, and to change the inclination angles twice a year (in early April and late August). The energy efficiency of the power plant is calculated in two stages. At the first stage the amount of electricity from solar panels per year when adjusting only the angle of inclination of the panels to the south is calculated. At the second stage energy efficiency of the power plant is calculated taking into account the increase of energy efficiency of the solar power plant when using the tracker system. The calculated electricity generation of the proposed solar power plant with tracker confirmed the efficiency and feasibility of using the designed tracker system. The application of the designed tracker system allows to increase the energy efficiency of solar panels by an average of 25%.

Water is a scarce natural resource fundamental for human life. Power plant architects, engineers, and power utilities owners must do everything within their hands and technical capabilities to decrease the usage of water in power plants. This paper illustrates the research carried out by Pöyry Switzerland to reduce the water consumption on power and desalination combined cycle power plants, on which there are gas turbine evaporative cooling systems in operation. The present study analyzed the potential re-utilization and integration of the heat recovery steam generator (HRSG) blowdown into the evaporative cooling system. Relatively clean demineralized water, coming from the HRSG blowdown, is routed to a large water tank, where it is blended with distillate water to achieve the required water quality, before being used on the gas turbine evaporative cooling system. To prove the feasibility of the HRSG blowdown recycling concept, the Ras Al Khair Power and Desalination Plant owned and operated by the Saline Water Conversion Corporation (SWCC), located in the Eastern Province of the Kingdom of Saudi Arabia, was used as case study. Nevertheless, it is important to mention that the principles and methodology presented on this paper are applicable to every power and desalination combined cycle power plant making use of evaporative cooling. Sea water desalination is the primary source for potable water production on Saudi Arabia, with secondary sources being surface water and groundwater extracted from deep wells and aquifers. Saving water is of utmost importance for power plants located in locations where water is scarce, and as such, this paper aims to demonstrate that it is possible to decrease the water consumption of power and desalination combined cycle plants, on which evaporative cooling is used as gas turbine power booster, without having to curtail power production. The outcome of the study indicates that during the summer season, recycling the HRSG water blowdown into the gas turbine evaporative cooling systems would result on the internal water consumption for the gas turbine evaporative coolers decreasing by 545 ton/day, or 23.79%, compared with the original plant design which does not contemplate blowdown re-use. Using evaporative cooling results on an overall gain of 186 MW, or 10.27%, on gross power output, while CO2 emissions decrease by 46.8 ton CO2/h, which represents a 13.8% reduction compared with the case on which the evaporative cooling system is not in operation. A brief cost analysis demonstrated that implementation of the changes would result in a negligible increase of the operational expenses (OPEX) of the plant, i.e., implementation of the suggested modification has an unnoticeable impact on the cost of electricity (CoE). The payback of the project, due to limited operating hours on evaporative cooling every year, is of 12 years for a 30 year plant lifetime, while 2.22 M USD of extra-revenue on potable water sales are generated as a result of implementing the proposed solution. Although in principle this value is modest, the effect of government subsidies on water tariffs as well as political and strategic cost of water is not included on the calculations. In conclusion, the study results indicate that water recycling, and reduction of plant's water footprint for power and desalination combined cycle plants using evaporative cooling, is not only technically possible but commercially feasible.

Hybrid systems in seawater desalination—practical design aspects, present status and development perspectives

3-E analysis of a Pressurized Pulverized Combined Cycle (PPCC) power plant using high ash Indian coal

Desalination of sea water through thermal and membrane based techniques and production of hydrogen through low temperature water electrolysis at facilities co-located with nuclear power plants are two areas identified for deploying co-generation projects in India in the near term. Nuclear desalination meets the requirements of clean drinking water in and around the nuclear facility, as well as to the in-house demand for high purity water for steam generation and other processes like hydrogen generation, coupled to it. Nuclear assisted hydrogen production also provides means to generate and distribute clean hydrogen which is envisaged as an important component of the decarbonized energy system of the near future. Currently the technologies for indigenous design, manufacture and quality assurance of desalination and medium scale compact water electrolysis plants are commensurate with the 220 MW(e) PHWRs presently operating in India. This work provides an overview of the research, development and deployment work carried out in these two areas in India, analyses the applicability of the IAEA Milestones Approach to nuclear cogeneration projects and discusses the problems and prospects of setting up and integrating more such facilities all over the country.

Most of the electricity produced throughout the world today is from steam power plants and improving the performance of power plants is crucial to minimize the greenhouse gas emissions and fuel consumption. Energy efficiency of a thermal power plant strongly depends on its boiler-condenser operating conditions. The low pressure end conditions of a condenser have influence on the power output, steam consumption and efficiency of a plant. Hence, the objective this paper is to study the effect of the low pressure end conditions on a steam power plant performance. For the study each component was modelled thermodynamically. Simulation was done and the results showed that performance of the condenser is highly a function of its pressure which in turn depends on the flow rate and temperature of the cooling water. Furthermore, when the condenser pressure increases both net power output and plant efficiency decrease whereas the steam consumption increases. The results can be used to run a steam power cycle at optimum conditions.

Coordinated Operation of Power Generation and Water Desalination

Provision for potable water is an important priority for the world population. Seawater desalination is a promising technology that can address this need. Currently, desalinated water is the main or supplementary source of water for numerous countries; the technology can also be used in other regions, facing geographical or economic water shortage. However, desalination is an energy-intensive process. This paper offers a new perspective on desalinated water cost reduction through coordinated operation of power generation and water desalination plants. The paper, first, models the energy consumption of water desalination plants. This model is integrated into a unit commitment problem that optimizes the commitment and schedule of power generators and desalination plants. The benefits of coordinated operation are quantified using this modified unit commitment model. Simulation results on IEEE 118-bus test system show that the proposed coordination framework can save 21% to 40% of desalination energy payments, depending on the flexibility of desalination plants. The cost reduction in real systems depends on the power grid specifics, location of desalination plants, water production requirements, and other factors. This paper suggests that coordinated operation may provide substantial cost savings and should be carefully considered.