0.94 → 0.99
.....
Raised power factor to optimise energy use and cut costs.
82.94 kVAR → 5.50 kVAR
.....
Reduced reactive power to boost system efficiency.
20% THDi → 10% THDi
.....
Minimised harmonic distortion to stabilise PFC performance.
Overview
South African farmers are grappling with the significant challenge of keeping their operations both efficient and profitable amidst the growing difficulties presented by loadshedding. The disruption in power supply not only jeopardises the continuity of farming operations but also leads to increased operational costs and potential loss of stock due to inadequate refrigeration.
The Challenge
The client, Christiana-based Calby Farming, was confronted with enhancing the efficiency and sustainability of their existing solar-powered grid-tied system. The underutilised system led to the interrupted operation of their cold rooms during loadshedding, requiring them to start up their diesel generators.
Challenge 1
Inefficient Use of Solar Energy:
Despite having a solar power setup, the existing grid-tied system failed to provide the necessary power backup during loadshedding. This inefficiency not only affected the farm’s productivity but also its ability to minimise labour and energy costs - a key motive behind the original solar installation.
The goal was to devise a solution that could leverage the full potential of the existing solar system, reduce dependence on generators, and ensure sustainable operations during loadshedding periods, all while keeping any additional financial outlay to a minimum.
Challenge 2
Dependency on Generators:
The main issue was the farm’s inability to use its solar system optimally - despite sunny conditions - during loadshedding. This led to a forced reliance on expensive diesel generators to maintain the operation of cold rooms. This had a significant impact on operational costs due to the high price of diesel.
The Solution
The solution, engineered by J&B Mechanical with support from ElectroMechanica, involved replacing all AC control components with systems that could operate on DC power. This included swapping out contactors for Variable Frequency Drives (VFDs). The proposed solution focused on four key aspects, namely:
Solar Panel and Voltage Optimisation
Restringing of solar panels to achieve the correct voltage, thereby maximizing the efficiency of solar energy capture and its conversion for farm us.Hybrid Control Panel Development
A control panel that seamlessly integrates solar power with existing utility and generator systems. This allowed for smart switching between power sources based on availability.Direct Current (DC) System Integration
Transitioning the entire power control system from AC to DC. This involved removing obsolete inverters and panels and introducing a new, comprehensive control box that prioritises solar energy as the primary power source, with the AC grid functioning as a secondary backup.Advanced System Components Installation
VFDs, Delta power supplies, and a programmable logic controller (PLC) to enhance system management. This setup allowed for the reutilization of existing solar panels, now restrung to match the optimised voltage requirements
Tech Overview
The core of Calby Farming’s solar modernisation included high-performance solar power units and sophisticated temperature sensor modules. These were complemented by smart control units and interfaces that facilitate seamless management and monitoring of storage conditions.
Temperature management is achieved with advanced temperature sensor modules. These provide realtime data to ensure products are stored under optimal conditions. The system is controlled via state-ofthe-art CPU modules and visualised through high-performance Human Machine Interfaces (HMIs) with Ethernet capabilities, enabling remote monitoring and control.
| Technology | Feature | Benefit |
|---|---|---|
| 24VDC CPU Module (PNP) | Central processing and control | Enhances system reliability and processing efficiency, enabling sophisticated control strategies for refrigeration. |
| DOP-100 7" Hi-Perf HMI Ethernet | Intuitive interface and connectivity | Offers operators easy access to system controls and monitoring, with Ethernet for remote access and alerts |
| 24VDC 8CH TC Temp. Sensor Module | Precise temperature monitoring | Ensures optimal preservation conditions by enabling accurate and responsive temperature control. |
| CLiQ II Power Supply 24VDC 960W 3PH | High-capacity and reliable power | Guarantees continuous operation of critical components, preventing downtime in refrigeration processes. |
| 24VDC 4xIN/2xOUT Analog Module | Integration of analogue signals | Facilitates the connection of various sensors and actuators, enhancing system flexibility and control precision. |
Results
The reconfigured system significantly impacted Calby Farming’s operations by enabling uninterrupted operation during loadshedding.
The system brought about immediate benefits: more consistent room temperatures were achieved by fully harnessing the sun’s potential and monitoring suction and temperatures to prevent cold room freezing. This not only extended and stabilised the cooling period but also significantly improved the system’s efficiency. Cost savings were immediately seen, as the system eliminated the need to run diesel generators.
The energy consumption of Calby Farming’s cold room was compared to neighbouring farm, Peacehaven. Peacehaven’s set-up includes 2 cold rooms with the same specifications as that of Calby, totalling 592 kW/h per day. By optimising the PC solution at Calby Farming’s single cold room, the solution saved 160kW/h* per day.
Peacehaven grid-linked system consumed 592.1 kW/h: 296.05 kW/h per cold room. Calby’s total consumption after the PV system was deployed was just 135.7 kW/h - a saving per day of 160.35 kW/h.