Objective: Mitigation Sectors: Renewable energy Collection

Table 1. Comparison of Solar and other Remote Watering Options

Pumping Technology	Advantages	Disadvantages
Solar	Low maintenance No fuel costs or spills Easy to install Simple and reliable Unattended operation System can be made to be mobile	Potentially high initial costs Lower output in cloudy weather Must have good sun exposure between 9 AM and 3 PM
Diesel or gas	Moderate capital costs Can be portable Extensive experience available Easy to install	Needs maintenance and replacement Maintenance often inadequate, reducing lifetime of system Fuel often expensive and supply intermittent Noise, dirt and fume problems Site visits necessary
Windmill	Potentially long lasting Works well in windy site	High maintenance and costly repair Difficult to find parts Seasonal disadvantages Need special tools for installation Labor intensive No wind, no power
Gravity	Very low cost Low maintenance No fuel costs or spills Easy to install Simple and reliable	Only feasible in a small number places
Ram	Very low cost Low maintenance No fuel costs or spills Easy to install Simple and reliable	Requires moving water as a operational necessity
Hauling	Lowest initial costs Excellent mobility	Very labor intensive

Status of the Solar Water Pump technology and its future market potential
PV water pumping has become a widely adopted solar energy technology in the last two decades (Firatoglu & Yesilata, 2004). Ten thousand PV water pump systems were installed worldwide up to the year 1993 (Barlow et al., 1993). This grew over sixty thousand systems by 1998 (Short and Orlach, 2003)
Rapid expansion over the last two decades of the global solar PV market has occured, with an average annual growth rate of 40 % (IEA, 2010) and 60% between 2004 and 2009 (REN21, 2010). A record 7GW of new grid-connected capacity was added in 2009, bringing total grid-connected capacity to 21GW with off-grid PV accounting for an additional 3 to 4GW. Crystalline silicon and thin film solar systems are in the early phases of rapid market deployment, and third generation and concentrated solar PV are currently in the R&D and demonstration phase.
While solar water pumps are much more small scale applications compared to PV technologies such as concentrated solar PV, the rapid expansion of PV technologies in general will benefit the deployment rate of solar water pumps. Since the main barrier to wide scale deployment of solar water pumps is the high initial capital costs due to the PV array, and the rapid expansion of PV technologies is leading to reduced prices for PV systems, it is expected that the solar water pump technology will reach higher penetration levels.
The IEA (2010) forecasts an average annual market growth rate of 17% in the next decade, leading to a global cumulative installed PV power capacity of 200 GW by 2020 and 3000GW by 2040 (with repowering of older systems). This would represent roughly 11 percent of global energy demand should this scenario play out. In terms of technology, the market share of thin films is expected to grow to 35% by 2013, due to constraints in the availability of high grade silicon.
Contribution of the solar water pump technology to developing countries social development
Solar water pumps contribute to social development in several ways. Since other remote water supply systems are less reliable than solar water pumps. The use of solar water pumps therefore provides a reliable, safe and adequate water supply which improves the community's health. Other benefits to social development are the improvement of social cohesion within the community, reduced migration out of the community, and increased community interaction in social events due to increased time availability (Short & Thompson, 2003).
In addition, in many developing countries there is a strong link between gender and water. In many developing countries, women are responsible for the water supply, spending a large portion of their time to gather the water. The use of solar water pumps can have considerable positive effects for women in these communities (Short & Thompson, 2003). The scope of these benefits is very broad. For instance, the adequate water supply improves the personal hygiene of women but also allows them to allocate more of their time to the other activities (Short & Thompson, 2003). After installation of solar water pumps women in these communities might allocate more time to activities such as education or foodgathering (WaterAid, 2001).
Contribution of the technology to protection of the environment
Solar PV systems, once manufactured, are closed systems; during operation and electricity production they require no inputs such as fuels, nor generate any outputs such as solids, liquids, or gases (apart from electricity). They are silent and vibration free and can broadly be considered, particularly when installed on brownfield sites, as environmentally benign during operation. The main environmental impacts of solar cells are related to their production and decommissioning. In regards to pollutants released during manufacturing, IPCC (2010) summarises literature that indicates that solar PV has a very low lifecycle cost of pollution per kilowatt-hour (compared to other technologies). Furthermore they predict that upwards of 80% of the bulk material in solar panels will be recyclable; recycling of solar panels is already economically viable. However, certain steps in the production chain of solar PV systems involve the use of toxic materials, e.g. the production of poly-silicon, and therefore require diligence in following environmental and safety guidelines. Careful decommissioning and recycling of PV system is especially important for cadmium telluride based thin-film solar cells as non-encapsulated Cadmium telluride is toxic if ingested or if its dust is inhaled, or in general the material is handled improperly. In terms of land use, the area required by PV is less than that of traditional fossil fuel cycles and does not involve any disturbance of the ground, fuel transport, or water contamination (IPCC, 2010).
While the use of PV technology provides several environmental benefits compared to traditional technologies, care should be taken that the installation of the solar water pump does not increase the use of groundwater so that supplies are depleted. Especially in the case where the initial capital costs are covered by a grant or other financial arrangement, the water supplied is more economical to the users compared to the original situation. This might increase water use. One approach to reducing this possible problem is to maintain water price for the users on the original level, and invest the extra money into a community development fund. For example, a solar water pump project in Thailand used the community development fund to invest in solar lighting systems.
Solar Water Pump Climate Benefits
When solar water pumps replace either diesel generated electricity or grid based electricity, there are certain climate related benefits. A diesel generator emits CO2 during operation and grid based electricity is usually generated with either coal, oil or natural gas which also emits considerable quantities of CO2. In contrast. a solar based water pump system does not result in greenhouse gas emissions. Extensive use of solar water pumps would therefore lead to substantial greenhouse gas emission reductions.
Financial requirements and costs of solar water pump technology
Several aspects of a PV pump system are key in determining the system costs:
a) size of the system. The high initial capital costs of the PV array is the major barrier to high penetration rates of the use of solar water pumps (Firatogly & Yesilata, 2004). The PV array is the most expensive part of the system. The size and capacity of the PV array considerably influences the up-front costs of the system. Therefore, it is important to use the smallest system size possible that still meets all the criteria of that particular location. Government or aid agency subsidies which cover the high initial capital costs are required in many locations to realize PV water pump systems (Short and Oldach, 2003). The high reliability of solar water pumps might offset its higher initial costs compared to diesel powered pump systems (Barlow et al., 2003).
b) insolation levels. This is direclty related to the required size of the system. The intensity and number of hours of sunshine determine the capacity requirements and thus the PV array size requirements. The more sunshine, the smaller the system requirements.
c) pumping head. The pumping head is the distance over which the water needs to be moved. The costs of water volume unit are proportional to the pumping head. Odeh et al., outline that a shallow well of only 20 meters depth compared to a deep well of 100 meters depth reduces water volume unit cost by around five times (Odeh, Yohanis, & Norton, 2006).
While system size and insolation levels greatly influence the capital costs of a PV water pump the operational costs of the system are generally very low due to low labor and maintenance costs. In contrast, inexpensive diesel or gas generators have low initial capital costs but require constant maintenance and the parts have shorter lifetimes which increases operating costs. This long-term economic advantage makes solar water pumping more cost-effective to conventional pumping systems, such as diesel powered pumps (NYSERDA, 2004). For example, a study investigating the economics of solar water pumps shows that in seven countries (Argentina, Brazil, Indonesia, Jordan, the Philippines, Tunisia, and Zimbabwe) solar water pump systems had a cost advantage over diesel pumping systems in the power range up to 4 kWp (Posorski & Haars, 1994; Posorski, 1996). A study by the Bureau of Land Management at Battle Mountain, Nevada, USA, showed that certain PV systems cost only 64 % over twenty years compared to a comparable diesel generator system did over ten years (NYSERDA, 2004). Additionally, the PV system required only 14 % of the labor hours that the diesel generator system required. The study by Odeh et al. found that PV water pumping systems are more cost-effective than diesel pumping systems for equivalent hydralic energy below 5750 m⁴ /day and 21.6 MJ/m2 day average insolation. In turn, diesel pumping becomes more economical for larger applications (Odeh, Yohanis, & Norton, 2006). This difference in costs over a long term is clearly illustrated in Table 2.
PV systems are particularly useful in locations to which it is not practical to extend the grid. Even in locations where connection could be made to a grid, utilities have found it more viable to use PV pumps than to extend and maintain the electric grid (Kou et al., 1998).