Water. desalination + reuse

February/March 2013

Water. Desalination + reuse

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TECHNOLOGY Renewable energy can provide desalination solution in MENA Excerpt from world Bank report* Editor's Note: The World Bank published a report in September 2012 on renewable energy in desalination in the Middle East and North Africa. The bank is currently working on organising a dissemination workshop, and D&WR will publish any further information on this on desalination.biz. What follows is an edited extract from the report's summary, which paints a picture of how renewable energy and desalination could be a match for the region. THE COUPLING of renewable energy (RE) sources with desalination has the potential to provide a sustainable source of potable water. However, the technical and economic potential of RE resources for power generation differs widely among Middle East and North Africa (MENA) countries. The annual potential of wind power, biomass, geothermal, and hydropower combined totals approximately 830 billion kWh. Although these resources are concentrated more or less locally and are not available everywhere, they can be distributed through the electricity grid to meet growing electricity demand. By far, the biggest resource in MENA is solar irradiance, which is available everywhere in the region. MENA's solar energy has a potential 1,000 times larger than its other renewable sources combined and is several orders of magnitude larger than the current total world electricity demand. The regions's potential energy from solar radiation per square kilometer per year is equivalent to the amount of energy generated from 1-2 million barrels of oil. This copious resource can be used both in distributed photovoltaic (PV) systems and in large central solar thermal power stations. While PV can economically generate only electricity, solar energy captured and redirected by mirrors to heat fluids - called concentrating solar power (CSP) - can generate both heat and electricity. Electricity cannot be stored as electrical energy, but heat can. CONCENTraTiNG SOLar POwEr CSP was selected for analysis in the current study for two reasons: 1. It has the potential to store heat so it can provide baseload for desalination 2. It has significant potential for technological improvement and significant cost reduction. With sufficient heat storage capacity, CSP potentially can provide baseload power 24 hours a day. The efficiency of today's solar collectors is .35 LCOE, $2010 per kWh .30 .25 B1 LCOE of CSP at DNI 2,400 kWh/m2/a .20 .15 B2 Peak-load LCOE B Medium-load LCOE .10 0 2010 Baseload LCOE B3 .05 Average LCOE without CSP 2020 2030 2040 2050 Figure 1. Electricity cost of concentrating solar powerplants for a fictitious case country in MENA compared with specific cost of peak-, medium- and baseload plants (annualized costs) Source: Trieb and others, 2011. Note: a = annum; B = break even with average electricity cost; B1 = break even with peaking power; B2 = break even with medium load; B3 = break even with baseload; LCOE (levelized cost of electricity) = LEC (levelized electricity cost);DNI = Direct Normal Irradiation. | 34 | Desalination & Water Reuse | February-March 2013 around from 8–16%, but by 2050, technical improvements are expected to increase efficiency to the 15–25% range. Currently, the solar energy collector field comprises more than half of the investment cost. Thus, improvements in collection efficiency indicate significant potential for cost reduction. However, despite its significant potential for development, CSP today is not economically competitive compared with conventional energy sources and most RE technologies such as wind and PV (Table 1). To mature and become cost-effective, CSP will continue to need strategic support. Such strategic support could be a combination of energy policy reforms to eliminate barriers, such as eliminating fossil fuel subsidies, creating an enabling environment for long-term power-purchase agreements and feed-in-tariffs, and supporting initial investments and R&D related to CSP. Based on assumptions adopted by this volume to develop CSP (Figure 1), the costs of fresh water produced by CSP thermal and RO membrane desalination plants vary considerably in the Mediterranean Sea, Gulf and Red Sea regions due primarily to differing seawater salinity. CSP-RO provides the lowest cost water in the Mediterranean and Red Sea regions, ranging from US$ 1.52–1.74 /m3 (Table 2). CSP-RO costs also vary depending on coastal or inland locations. Inland, higher solar radiation may reduce costs by as much as US$ 0.15 per m3. Figure 1 shows the applied strategy for a fictitious case country in MENA. Annualized costs of fossil-fuel power generation are expected to increase in the future. Thus, the current cost of peaking power is projected to rise from its present US$ 0.21/ kWh to more than US$ 0.35/kWh by 2050. Medium- and baseload power will be less expensive, but will follow a similar trend. In contrast, present CSP costs of approximately US$ 0.28/ kWh are expected to fall to approximately US$ 0.08 /kWh by 2050. Starting a CSP project in 2011 could have * Renewable Energy Desalination: An Emerging Solution to Close the Water Gap in the Middle East and North Africa; MENA Development Report; download from www.worldbank.org/MNA/watergap.

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