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.
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.
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.
The major findings of this energy audit are twofold:
- Technical improvements can be made to improve the energy efficiency of the facility. These steps are summarized in the table below.
- 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.
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:
- 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.
- 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.