Water Flowing

Irrigation of crops is critical to agricultural success, but in Senegal, this task is usually done by hand and can take all day. High fuel costs make gasoline pumps unaffordable and initial investment costs of stand-alone solar are too high for small scale farmers. The Sustainable Engineering Lab, as part of Powering Agriculture: An Energy Grand Challenge for Development Initiative, is piloting research in the Millennium Village of Potou, to reduce the price of energy for farmers by introducing solar PV as a reliable and cost-effective alternative.

The Niayes zone of Senegal is responsible for more than half of the country’s horticultural production. Finding a way to reduce production costs for farmers in this area can potentially lead to major economic gains.

The Sustainable Engineering Lab (SEL) has launched an innovative batteryless solar PV irrigation system in northern Senegal. The centralized 6.8kW solar array provides distributed 3-phase AC power to seven horticulture farmers that have their own shallow wells and 1-hp AC pumps. Our pre-paid smart-control system distributes energy to individual pumps as it becomes available throughout the day, enabling us to meet irrigation demand without the high capital and recurring costs of battery storage. Farmers maintain their existing gas-powered pumps as backups but we have set the price of solar energy slightly lower than the price of gasoline so that the farmers opt for the cheaper solar.

solar_ag_how_it_works

Centralized solar & monitoring
Electricity is generated centrally by a single, solar PV array. A custom-made battery-less AC system controls and monitors pump function for 7+ farmers.

Pre-paid credit
Electricity is sold by a micro-utility to farmers using a pre-paid credit system similar to cell phone scratch card systems, only paying for what they consume.

Decentralized pumps
Farmers retain autonomy of their individual wells and pumps.

Benefits

Fuel and Time Savings
Farmers typically spend $1/day on fuel for gasoline-powered irrigation pumps. These pumps are over-sized and consume more gas than necessary. Properly sized AC pumps require less energy to meet the same crop water requirements. Fuel and time are also saved on transportation, as the closest gas station is about a one-hour drive from the village.

Environmental Savings
The gasoline-powered pumps produce approximately 2.4kg of CO2 per liter of gasoline—0.24 tons of CO2 in a typical 100-day season per farmer. Additionally, fuel spills are common. Switching to solar will eliminate both sources of pollution.

Project Innovations

Grid compatible AC pumps
Unlike DC, not only are AC pumps compatible with a future grid connection, but excess AC power could be a potential and profitable energy supply for domestic and commercial customers, who use AC versus DC appliances.

Distribution of electricity to decentralized pumps
Centralized electricity production, with decentralized distribution allows farmers to retain autonomy of their own wells and pumps and creates a model for micro-utilities that can be scaled up beyond irrigation to meet other demand.

Battery-less systems
The system is built without the need for a battery to keep capital and recurring costs low. To do this, SEL collaborated with an Indian manufacturer to engineer a low-cost alternative to standard inverters. The new inverter is designed to work in off-grid markets such as our pilot site, Potou, Senegal.

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Project Timeline

2013

October
USAID awards SEL with $1.1M innovation grant [Blog Entry]

November
Preliminary visit by SEL team to Senegal to select the beneficiary community and identify potential technical partners

2014

January / February
Local launch of project and community meetings [Blog Entry]

June
Arrival of pump controller in NY for testing [Blog Entry]
Watch demo

October
Pump controller shipped to Senegal for pilot testing [Picture tweet]

October / November
SEL team travels to India to meet with pump controller manufacturer and other potential suppliers of pumps, solar tracking units and smart meters. [Blog Entry]

December
Installation of solar PV array and pump testing [Blog Entry]

2015

February
Farmers begin using solar PV irrigation system
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