Energy Assessment on fruit & vegetable farm

Fruit and Vegetable Farm

Background

The client is a large farming operation in the Eastern Cape where citrus fruit and vegetables are produced.   Due to confidentiality purposes the name of the client cannot be revealed.

Energy sources used for the farming operations include electricity for irrigation pumping systems and housing, and diesel fuel for farming equipment, such as tractors and trucks, for the transport of produce.

The Issue

The client had grown its farming operations very rapidly over the past 5 years by using a very scientific farming approach.  New farms were developed and pumping stations were built at very remote locations. The steep increases of electricity costs during recent years and the responsibility towards greenhouse gas emissions were the main reasons for the owners to request an energy audit.

Energy Audit Methodology

Electricity is supplied at 19 Eskom points.  A cost analysis was done to determine whether the most suitable tariff structures were being used.  The costs were benchmarked against a sample of similar supply points to determine cost saving opportunities.

The electricity consumption was analyzed and split into major consumption groups, as given in the graph below.   It shows that 82% of the electricity was used for irrigation pumping systems – the most significant energy user.

Farm_Pie

The electricity consumption was split between citrus and vegetables and benchmarked against other similar farming operations.  The fuel consumption was also benchmarked against other citrus producers.  The fuel storage and supply procedures were audited to assure that all fuel purchases were accounted for and that control procedures were in place.  Maintenance procedures of the equipment using fuel were also audited.

Major Findings

The energy analysis was done for the period March 2012 to February 2013.  A total of 1,173,213 kWh of electricity was used at a cost of R1,25m.  During the same period 302,118 litres of diesel was used at a cost of R2,9m.

The control procedures for fuel were found to be very good.  The benchmarking results show that the electricity use was higher than the average of the sample of farms that was used for comparison.  The rest of the findings are explained in the summary of the action plan below.

Proposed Action Plan

  • Pumps
    • Optimize on pumping curve
    • Plotting values for each block
    • Take action where necessary
  • Housing, Offices, Stores, Packhouses
    • Replace lights with efficient alternatives when due
    • Install solar water geysers
  • Fuel
    • Consider packhouse at Addo to reduce logistic distance
  • Electricity Cost
    • Reduce Peak time on Ruraflex (pumps, timer for cold store)
    • Change large points to Ruraflex
    • Investigate Landrate cost/kWh exceptions
    • Combine small Landrate points
  • Renewable Energy
    • Measure benefits of the Solar and Wind solution at SR561
    • Consider Solar PV solutions for Badlands, Loftus or Falcon Gat
  • Energy Management
    • Centralize energy management (“Energy Manager”)
    • Improve Energy Information System
      • Update monthly for early warning
      • Review annually for updated action plan
    • Sub metering
      • Isolate houses, pumps, cold store and other facilities
    • Determine Energy Performance Indicators (EnPI)
    • Measure Improvement against baseline
    • Follow principles of ISO50001

 Actions taken by the Farm:

  1. A pumping system optimization exercise was done as a follow-up audit by using a portable flow meter and comparing results on the pumping curves and the PSAT optimisation software. A sample of 18 pumping systems was evaluated out of the total of 39 pumps.  The efficiency ratings of the pumps were found to be from 39% to 78% with the average around 60%. Recommendations were made to improve the efficiency by altering the application sizes, changing pumping impellors or installing VSD’s.  The changes will increase the total efficiency rating to 80% and save R200 000 in electricity cost per year.  The investment cost is estimated to be R90 000.
  2. The client changed one electricity point to a Ruraflex tariff structure which will save 15% of electricity cost with no investment costs. Other cost saving initiatives are still being investigated.
  3. A solar PV analysis was done for the client at one of the locations. Over the next 25 years the PV solar will cost an equivalent of 42c/kWh, compared to the current Eskom fee of R1.05/kWh and still rising each year. This would, however, require a high capital investment and the client is still evaluating the funding options.
  4. An energy management information model was developed and implemented at a cost of R25 000. This model will absorb the electricity and fuel consumption and cost, the production of crops and the rainfall variables and provide reports on the energy performance of the business on a monthly basis. This information can then be used to revise the action plan, motivate improvements and monitor the future energy performance against the 2012 baseline.