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.

Apple packhouse

Background

The client is a large apple packhouse operation in the Western Cape where apples are stored, sorted and packed for the export market.   Due to confidentiality purposes the name of the client cannot be revealed.

The main energy source is electricity obtained from Eskom.  Apples are harvested by farmers during February to April and then stored in controlled atmosphere cold stores for up to 10 months at the packhouse facility.  Short term storage is done with regulated atmosphere cold stores and forced air cooling for packed pallets.  The cold storage and packing operations continues throughout the year.

The Issue

A previous energy audit was done at this client during 2010.  One of the recommendations was to implement an energy information model for better energy management.  This model was implemented and maintained during 2012 and 2013.  The client requested a second energy audit during 2013 to assist with the development of a detailed action plan.

Energy Audit Methodology

Information gathered in the energy model was analyzed to obtain a better view on the electricity consumption patterns in the facility.  The assessment was done for the electricity consumption period from January 2012 to December 2012.  During this period almost 7.1GWh of electricity was used at a cost of R4.59m, an average unit cost of R0.67/kWh.  The electricity balance (see below) shows that 89% of the electricity is consumed in cold storage operations.  The client agreed that this significant energy user should be the focus point of the improvement action plan.

Apple_Pie

A checklist was compiled from literature on best practices for energy efficiency in refrigeration applications.  This checklist was followed as a guideline to evaluate all the cold storage operations at this packhouse as an input towards developing the improvement action plan.

Major Findings

The major findings of this energy audit are twofold:

  1. Technical improvements can be made to improve the energy efficiency of the facility. These steps are summarized in the table below.
  2. It was clear that there was a lack of energy management skills at the packhouse. The energy information was gathered in the model, but nobody really attended to the information and acted upon it. The audit also indicated that some of the information was not correctly captured, which may lead to false conclusions.  The technical people were found to be very competent in running the cold stores, but during their busy season they do not have time for energy management activities.

Proposed Action Plan

The proposed technical action plan is summarized in the table below.  These actions would require an investment of R390 000 and will lead to an energy saving of R1.35m per year.  The projected saving of 1.84GWh per year is a saving of 26% on the electricity consumption of the packhouse facility.

apple_table

A good energy management approach is essential for sustainable energy improvement.  The packhouse has implemented sub metering and an energy information model to assist in energy management. The information should provide a baseline against which performance improvement can be measured.  The following improvements to this approach were recommended:

  • Determine the roles and responsibilities for energy management at Valley.
  • Revise the data for 2012 and establish a baseline.
  • Revise the data for 2013 and determine improvement against the baseline.
  • Set improvement targets for 2014 and beyond.
  • Continue with short interval control during 2014 based on weekly results.
  • Allocate resources for the energy management actions or subcontract.

A solar PV analysis was done for the packhouse.  A 741kWp system is recommended before excess power is fed back into the grid.  This system will cover 5200 square meters of existing roofing space. The total investment cost is R9,6m after tax rebates.  The costs of the proposed solar PV system equates to effectively paying only 34.7 cents/kWh over the next 25 years.  The projected average cost of electricity obtained from Eskom is R2.66 /kWh over the next 25 years.

Actions taken by the Packhouse:

  1. The outcome of the energy audit was received with great appreciation by the packhouse. The action items requiring capital investment were put on the budget for next year.
  2. The packhouse is also negotiating with an outside energy consultant to assist with the energy management process during next year. This will include the energy projects for improved refrigeration control.