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

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  – 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

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 . 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.  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 .

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)  – 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 . 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 .