SUPPLY AND INSTALLATION OF SOLAR AND HYBRID SOLAR WATER SYSTEM

Tenders & Other Advertisments
1

Samaritan’s Purse wishes to contract a legally recognized service provider (company) to Supply and Install Solar and Hybrid Solar Water System: Details below
RFQ-Supply and Installation Of Solars and Hybrid Solar Water System.pdf (313.8 KB)

2

I am very concerned about your tender for solar power in Bunj, a town I know well, after a colleague forwarded to me the RfP today. It is not rational, will be hard to monitor, will be unstable, and will not last long. I detail this below:

  • 34 x 325W = 11kW solar panels are neither better nor worse than 265W, 280W, 300W, 330W, etc. but they will be very hard to source. An equivalent 11kWp array of another wattage is easy to achieve and might work better with the particular amperage and voltage of a given charge controller. This array is too big for your charge controller.
  • 24 x 12V 200 Ah Deep Cycle Batteries means that you will have 6 strings of 4 batteries in series to achieve a 48V battery bank. Two strings is better, and 1 is best. 6 is terrible for having a balanced battery bank, as peculiarities in the resistance will over charge some and undercharge others.
  • 24 x 12V x 200Ah = 57600kWh energy storage, which is easily achievable with 2V Rolls batteries I recently installed for AECOM in Aweil (24 x 2V x 2160Ah = 103680kWh), this battery bank will be bigger, but that is what you need for longevity in hot temperatures.
  • Addiitonally, if you specify 200Ah batteries, unscrupulous bidders in Juba will supply you with Su-Kam and/or Gaston batteries, which will only last 1-3 years under conditions in South Sudan. See chart below.
  • The Studer VS - 120 A Vario String MPPT charge controller, Solar inverter Fronius 8.2 - 1 (8000 W), 10000 Watts V ictron inverter charger is a mixture of three different manufacturer’s equipment and will not be possible to monitor with the Victron Color Monitor. Normally, a Victron charge controller should be used.
  • The maximum wattage recommended on the VS-120 is 7,000W, and you specify 11,050W. (http://www.studer-innotec.com/en/products/variostring-series/vs-120-312)
  • The combination of AC coupled Fronius inverter and DC coupled Victron inverter charger is a complex system that is not common to South Sudan and will be unstable. These systems are possible when a client already has an AC coupled (grid-tied) Fronius inverter, for example at a house in Germany, and wishes to install a separate inverter charger with a battery bank to keep some loads online if the grid goes down. However, it is not a rational solution for a remote site in Bunj.
  • You have omitted important components such as fusing, disconnects, generator auto-start, and a monitoring system.

I recommend you either rewrite the tender BoQ, or allow for alternatives, so that a qualified engineer can provide you a rational system.

1 Like
3

Additionally, on the solar water pumping project, SP should provide the well parameters: yield in liters per hour, depth to dynamic water level, distance from well to water tank, and diameters of delivery pipe and well. Then, a qualified engineer can verify the pump presented in the BoQ, and specify an alternative from Lorentz in the case that this pump is not available or is not the most efficient solution.

Typically, 5-10 pumps will provide the required water flow, but only one is ‘best’, defined by efficiency in water pumped per Watt of power from the modules. In addition, some applications may utilize a larger number of modules so that pumping starts earlier in the day and lasts longer into the afternoon. This may result in 10-40m3 of additional water per day in many South Sudan applications.