Improved Water Management

REDUCING CARBON EMISSIONS ON FARMS WITH IMPROVED WATER MANAGEMENT

Previous CCC industry trend reports have indicated that electricity consumption for the pumping of water is the largest source of farm-level carbon emissions. Irrigation of crops is a necessity in a water-scarce country and predominantly coal based electricity is used as an energy source for pumps. Improved water management has the purpose of saving water, cost and reducing carbon emissions. The following opportunities for savings have been obtained during irrigation pumping system assessments on fruit farms.

The starting point is to determine the “correct amount of water” for each tree or hectare. Too little water may reduce the production output and fruit quality, while too much water is a waste of water and energy cost. A study of water flow rates on one farm has shown that some orchards receive only 50% of the intended water supply while other orchards have received 50% more than target. A system to monitor the soil moisture contents is a necessity for good water management on farms.

A lot of water is wasted by evaporation during the irrigation process, mainly due to wind and heat on the ground surface. Improvement in irrigation technology to reduce evaporation losses can save up to 40% of water and related pumping energy.

The irrigation pipe diameters, piping network and geographical height determines the head and flow rates that the pumps are operating on. Higher water pressures require more energy and the irrigation design should attempt to maximize flow and minimize the pressure required. Many cases were identified where the pump head could be reduced significantly with improved piping and irrigation system, while still providing the required water flow rate.

The operation (pressure and flow) of the pump is determined by the irrigation network design. The selection of the pump and the condition of the pump determine the ability to convert electrical energy into the pressure and flow. The efficiency of a sample of pumps were tested and the results show that the pumps use on average around 30% more energy than needed for the required head and flow.

Pumping of water from boreholes has also shown significant losses due to inefficient borehole pumping systems. A sample of 11 boreholes on one farm consumes an average 0.35kWh per cubic meter. The average consumption of 28 other boreholes at similar borehole depths was 0.62kWh per cubic meter. This shows that the potential energy (and carbon emission) savings in improved borehole pumping systems can be as high as 50%.

Larger farms have water distribution networks where water is pumped from rivers, boreholes and dams to other dams or orchards. Sometimes water is pumped 3 times before it reaches the orchard, while each pumping operation adds to the total energy consumed. The sizes and locations of the dams and the relevant position between the dams and the orchards all have an impact on the total energy requirements for the water distribution network. The water distribution network should be optimized by selecting the lower energy boreholes and pumps to do most of the work where possible. This is a more complex and strategic approach towards energy optimization and can also be used to determine the position and sizing of future dams in the network.

The results obtained from the case studies discussed above are not visible to most farm managers and a technical analysis of the pumping systems are required to identify saving opportunities. It is however clear that an average cumulative saving of 30% to 50% on carbon emissions is possible with improved water management techniques on farms.

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.

Energy well spent

Energy well spent

EnergyWellSpent_5aAlthough it is impossible to arrive at a single figure, one can safely say that energy is a major input cost for the fruit export industry. It is also the cornerstone of the cold chain. The combination of keeping costs down and production up is reason enough to invest energy into energy efficiency.

IN 2008, South Africans were shocked into a new appreciation of electricity. For the first time we could remember, load shedding was a part of our lives. As the national electricity utility struggled to keep the lights on, both households and industry had a taste of life without power.

Although load shedding did not cause significant fruit losses, the export industry wisely decided to heed the warning. Further motivated by substantial electricity tariff increases and global pressure to reduce the industry’s carbon footprint, an energy benchmarking project was launched under PHI-1 in 2008.

EnergyWellSpent_6aThe aim was to develop and implement a benchmarking system for energy consumption on farms and at pack houses and cold stores to improve electricity and fuel efficiency. Koos Bouwer, from KBC Industrial Engineers, was appointed to oversee and coordinate the project.

“The benchmarking results showed that it was virtually impossible to make generalisations about energy use in the industry,” says Koos. Not only did the different facilities’ energy use vary widely, they also paid vastly different tariffs – from less than R0.40 per kilowatt hour (kWh) to more than R1.40 per kWh. The best performing pack houses used around 15kWh of electricity per ton of fruit packed, while others used three times as much.

It was also clear that the different methods of cold storage had different energy implications. Storage of apples in a controlled atmosphere was extremely efficient at less than 1kWh per ton of fruit per day, whereas fruit packed in cartons on pallets used almost 8kWh of electricity per ton per day. “The important conclusion drawn from these varying results was that there were many opportunities for energy efficiency improvements,” says Koos. “If one pack house could be more efficient, there was no reason why others couldn’t.”EnergyWellSpent_1a

FROM “WHERE ARE WE” TO “WHAT CAN BE DONE”

EnergyWellSpent_3aIn 2012, the United Nations Industrial Development Organisation (UNIDO) approached the South African government to take part in its Industrial Energy Efficiency (IEE) improvement project. Funded by the Swiss Secretariat for Economic Affairs and the UK Department for International Development, the local IEE project is hosted by the South African National Cleaner Production Centre (NCPC-SA) at the CSIR. The IEE project focuses on five industry sectors, including agro-processing. Under the project’s auspices, the NCPC-SA agreed with PHI-2 to conduct fully subsidised energy audits at interested pack houses and cold stores in the fresh fruit industry. The coordination task was again entrusted to Koos. “The process we followed was more an assessment than an audit,” says Koos. “Instead of looking at how facilities adhered to standards and specifications, the consultants assessed energy use and trends.” The difference between audit and assessment is also clear from the stated purposes of the project:

  • Assist to quantify energy consumption at a facility and identify the significant energy users.
  • Identify opportunities for the reduction and more efficient use of energy in the plant as part of an energy management plan.

The energy efficiency audits initiative was rolled out in January 2012 when Koos embarked on a campaign to raise awareness in the industry. He arranged several regional workshops where NCPC-SA representatives explained the nature and process of the project and recruited participants. Companies that wanted to participate signed a memorandum of agreement with the NCPC-SA. A total of 29 pack houses and cold stores agreed to take part. The NCPC-SA assigned trained energy consultants to spend three to four days at each of the participating facilities. The audit was fully subsidised by the NCPCSA. All the participants had to contribute was their cooperation. Once the audits were completed, the energy consultants discussed their detailed reports with the owners of each individual pack house and cold store. The reports highlighted, among others, savings options, results on feasibility, quantification of behavioural changes and the expected payback periods for energy saving investments.EnergyWellSpent_2a

THE FINDINGS

The 29 participating facilities had a combined energy use of 101.1 megawatt hours (MWh) of electricity at a cost of R77 million for the year 2011. The energy audits revealed that they could save a combined 27MWh per year, putting R20.7 million back into their collective pocket. This 26.8% saving would require an investment of R26 million that will, on average, pay for itself in only 1.26 years. The potential electricity saving equals a reduction in CO2 emissions of 27 000 tons per year.  Some of the areas in which considerable efficiencies can be gained are energy efficient lighting, variable speed drives and energy management systems. The single biggest opportunity, however, is to improve the efficiency of cooling equipment.

THE WAY FORWARD

Koos points out that it is important to understand that the facilities are all unique and that the same change will have different impacts at different facilities. “It is literally impossible to generalise because one size does not fit all. The only way to improve facilities’ energy efficiency is to use individual energy audits or assessments as the starting point.” A number of the facilities who took part in the audits are doing just that. Using their site-specific recommendations, they have started to implement the suggested energy efficiency measures and are reaping the benefits. “The project seems to have acted as a catalyst,” says Koos. “It made the saving opportunities visible and facility owners are acting on it.”

© Koos Bouwer Consulting 2014

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.