Water Pumping and Groundwater Depletion - Comparison of Different Energy Sources for Water Pumps: Grid, Solar and Diesel

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Introduction

When comparing grid connected, diesel powered and solar water pumps different parameters have to be taken into account.

For the decision which energy source the water pumping system should run on, externalities, which are mainly of ecological nature, are almost never taken into account. Therefore ecological benefits are commonly not decision-relevant for farmers. The reason could be that external effects and environmental consequences of groundwater pumping are harder to observe than private economic costs and benefits. Even though monetization of external costs could be a valuable step, farmers in developing countries – where by far the highest share of irrigated area is located [1] – do very often not have the freedom to care about environmental arguments which is a plausible reaction when struggling with the non-availability of sufficient food.


Advantages and Disadvantages of Grid Connected Systems

Disadvantages

Economic Aspects

Under economic aspects the grid connected solution is an alternative which can be taken into account only under the precondition that a grid connection is already available before the water pumping project is planned. If that is not the case, like in large parts of the world, then the grid connected water pumping system won’t be feasible. In Sub-Saharan Africa, more than 600 million people across almost 50 countries have no access to electricity and in India this number is around 300 million [2]. Also in remote areas in rich countries like the US, an extension of the power supply is either too expensive or not feasible because of natural conditions. Meah et al. [3] state that the cost of extending a distribution line run from 10,000 USD to 16,000 USD per km. This is clearly too much to pay for a farmer or any other end-user especially considering that not only the building costs have to be covered but also the maintenance of the line has to be ensured. People who benefit from remote water pumping could not pay for these costs either [4].


In addition to the costs of setting up and maintaining a distribution line, comes the problem of an unreliable grid in many countries. In western and southern India for instance – the country with the largest irrigated area (39 million hectares) [5] – the government has subsidized electricity for irrigation purposes. It is available at very low (one or two cents per kWh) to no cost and therefore provided irregularly during off-peak periods. This provision of heavily subsidized electricity leads to groundwater over-pumping [6][7]. The off-peak periods are usually during night time, when it is dangerous and unproductive to be outside on the fields. The irregular access to energy forces the farmers to grow low value crops that can tolerate infrequent water supplies keeping them financially dependent on the subsidy. Besides, the utilities make no money in this distorted market and have no incentive to approve electric water pumping applications leading to a pent-up demand. Also no incentive to increase the efficiency of electric pumps is given with the effect that electric pumps show an efficiency range of 15-20%. This is highly wasteful knowing that 75% efficiency is attainable [7].


Environmental and Social Aspects

From an environmental point of view, grid driven water pumps can only be sustainable, if the electricity is produced with as little as possible emissions because the emissions of various gasses emitted by combustion of fossil energy sources like coal is related to climate change as well as health hazards [8]. Staying with the example of India, this is not the case. The largest share of electricity production is covered by coal (60%) and only 15% by hydropower [9]. In the International Energy Outlook 2016, coal has also worldwide the largest share of electricity production (40% in 2012). In the report’s reference projection it won’t be until 2040 that renewable generation surpasses coal as the source of electricity generation with the highest share [10].


Advantages

On the other hand grid connection allows for the possibility to sell excess energy produced by stand-alone systems back to the grid. This is a very effective method to minimise water pumping and use energy efficiently. Combining a solar pump with grid connection would be an ideal concept to counteract groundwater over-exploitation [6]. The precondition of an already existing grid connection is of important because of the above mentioned high costs of extending the distribution line.


Conclusion

In conclusion it can be stated that grid connected water pumps are only a suitable option if first, a grid connection already exists at the water pumping installation side, second, the electricity supply via the grid is stable and third the energy supplying the grid is mainly if not entirely produced out of renewables. As outlined these conditions won’t be met either easily or soon and therefore alternative systems of power generation are needed.


Comparison of Solar Powered and Diesel Powered Water Pumping Systems

Stand-alone systems like solar and diesel can improve rural electrification [11] and in the following these two systems are compared.

References

  1. ↑ FAO, 2012. World Agriculture Towards 2013/2050: The 2012 Revision (No. 12–3), ESA Working Paper. Global Perspective Studies Team. http://www.fao.org/docrep/016/ap106e/ap106e.pdf.
  2. ↑ Brent, W., 2017. India: Ground zero for scaling electricity access and SDG7. http://www.powerforall.org/blog/2017/8/8/india-ground-zero-for-scaling-electricity-access-and-sdg7.
  3. ↑ Meah, K., Fletcher, S., Ula, S., 2008. Solar photovoltaic water pumping for remote locations. Renew. Sustain. Energy Rev. 12, 472–487. doi:10.1016/j.rser.2006.10.008. https://www.researchgate.net/publication/222015334_Solar_photovoltaic_water_pumping_for_remote_locations.
  4. ↑ Al-Smairan, M., 2012. Application of photovoltaic array for pumping water as an alternative to diesel engines in Jordan Badia, Tall Hassan station: Case study. Renew. Sustain. Energy Rev. 16, 4500–4507. doi:10.1016/j.rser.2012.04.033. https://www.researchgate.net/publication/257548417_Application_of_photovoltaic_array_for_pumping_water_as_an_alternative_to_diesel_engines_in_Jordan_Badia_Tall_Hassan_station_Case_study.
  5. ↑ Worldwatch Institute, 2016. Global irrigated area at record levels, but expansion slowing . http://www.worldwatch.org/global-irrigated-area-record-levels-expansion-slowing-0.
  6. ↑ 6.0 6.1 CGIAR, 2015. Sunshine: India’s new cash crop (Research Program on Water, Land and Ecosystems). Colombo. https://wle.cgiar.org/cgspace/resource/10568-68664.
  7. ↑ 7.0 7.1 Kelly-Detwiler, P., 2014. SunEdison: The global market for solar irrigation is almost limitless. Forbes. https://www.forbes.com/sites/peterdetwiler/2014/04/04/sunedison-the-global-market-for-solar-irrigation-is-almost-limitless/. Cite error: Invalid <ref> tag; name "Kelly, 2014" defined multiple times with different content
  8. ↑ Kaundinya, D.P., Balachandra, P., Ravindranath, N.H., 2009. Grid-connected versus stand-alone energy systems for decentralized power: A review of literature. Renew. Sustain. Energy Rev. 13, 2041–2050. doi:10.1016/j.rser.2009.02.002. http://www.sciencedirect.com/science/article/pii/S1364032109000483.
  9. ↑ OECD, IEA, 2015. India Energy Outlook, World Energy Outlook Special Report. Paris. https://www.iea.org/publications/freepublications/publication/IndiaEnergyOutlook_WEO2015.pdf.
  10. ↑ U.S. Energy Information Administration, 2015. International Energy Outlook 2016, with Projections to 2040. Washington, DC. https://www.eia.gov/outlooks/ieo/.
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Kaundinya, 2009
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