The Ministry of New and Renewable Energy (MNRE) is seeking feedback from the public and stakeholders on the preliminary design specifications for solar cold storage (SCS).

The storage capacity of the SCS, ranging from 2 MT to 10 MT, is intended to be exclusively powered by solar photovoltaic as a distributed renewable energy source (DRE).

The parameters for SCS have been determined to enable installation at any site across India. The guidelines and specifications are primarily designed for storage and preservation facilities within the temperature range of 4°C to 15°C, catering to both perishable and non-perishable commodities such as fruits and vegetables.

The proposed specifications aim to meet all CSC and cooling requirements outlined in the National Horticulture Board standards.

The operational life of the SCS system should be a minimum of 10 years from the date of commissioning.

The SCS system utilizes a solar module array to convert irradiance into DC electrical energy, powering the refrigeration unit. This DC power drives the refrigeration system, providing cooling for products stored within a cold chamber.

The inclusion of a Maximum Power Point Tracker (MPPT) is essential to optimize power utilization from the module array, maximizing input for the refrigeration unit and battery charging.

The controller, mandated to have protective features, must be housed in a cabinet with a minimum IP-65 protection rating. Adequate safeguards within the controller are imperative to ensure the protection of the solar cold storage system.

Electric Battery Bank for Auxiliary Components: The auxiliary power system incorporates various equipment, including displays, controls, fans, sensors, RMU, protection circuits, and alarms. Within the system, multiple battery banks are deployed to supply power to auxiliary electrical loads such as evaporator unit fans, TES control panel, temperature controller unit, lighting, and the data monitoring system.

Engineered for a 2-day autonomy period, the battery bank ensures uninterrupted power for essential functions during unforeseen circumstances.

Solar Photovoltaic Array

The Solar Photovoltaic (SPV) arrays are composed of modules with identical capacity, type, model, and specifications, connected in series or parallel to achieve the required voltage or current output.

The recommended operational capacity for the SCS system is between 4KWp and 12KWp, measured under standard test conditions.

The controller power capacity should align with the solar panels’ power capacity rather than the compressor capacity. Additionally, the Power Point Tracking (MMPT) system is designed to exclusively track power, not voltage, at the maximum power point, with a minimum MPPT efficiency of 95%.

The controller must have at least IP54 protection or be housed in a cabinet with a minimum IP65 protection level. An isolator switch is strategically placed between solar panels and the controller.

The integration of GSM/GPRS includes geo-tagging, and associated charges are included in the costing until the end of the pump set’s warranty period. For details on individual PV modules, manufacturers should adhere to MNRE specifications under the KUSUM program.

Module Mounting Structures and Tracking System

The mounting of PV modules involves robust metallic structures designed to withstand module loads and high wind velocities (up to 150 km per hour).

An optional seasonal tilt angle adjustment is provided three times a year to enhance the performance of the SPV array in SCS systems. Hardware for structure fitments, such as SS 304 or 8.8-grade materials, is recommended, and modules should be secured with anti-theft bolts of SS 304 Grade.

For ground-mounted modules, the foundation design adheres to site-specific conditions, referencing relevant IS standards (IS 5624, IS 6403, IS 456, IS 4091, IS 875). These specifications are indicative of minimum standards, allowing manufacturers/implementing agencies flexibility to adopt higher standards for enhanced performance.

Earthing Arrangement

Earthing arrangements follow provisions for the chamber compartment, refrigeration unit, compressor, and condenser, with separate earthing for the controller, refrigeration unit, and SPV array.

Safety measures ensure earthing capability for leakage current during installation, and a lightning arrestor is provided with every solar cold storage system. Separate earthing is recommended for the AC Side (compressor/AC supply), DC Side (structure/controllers/modules), and lightning arrestor to enhance safety.

Guarantee of Performance

The SCS system’s nominal cooling rate performance is guaranteed under the “Average Daily Solar Irradiance” condition of 4.0 kWh/m2 (low irradiance) on the global horizontal plane.

This assurance relies on the utilization of electrical energy generated by the SPV array of modules. It’s important to note that the actual cooling energy produced on a specific day may vary based on factors such as solar intensity, location, array tilt, season, etc.

Manufacturers commit to guaranteeing SCS systems against defects in material and workmanship under normal use and service for a minimum of 10 years from the date of commissioning.

The warranty for modules extends to an impressive 25 years. As part of their commitment to ensuring trouble-free operation during the warranty period, manufacturers are required to provide a comprehensive list of spares.

The SCS used must be securely marked with the following parameters declared by the manufacturer:

Refrigeration Unit

• Manufacturer’s name, logo, or trademark
• Model, size, and SI No of pump set if used (To be engraved/laser marked on the motor frame)
• Compressor & Condenser Rating (TR/ HP/KW)
• Total storage capacity (CM/Cf)
• Operating Temperature Range
• Type: Refrigeration Unit
• Photovoltaic Array Rating in Watts Peak (Wp)
• Country of origin

Controller

• Manufacturer’s name, logo, or trademark.
• Model Number
• Serial Number
• Voltage Range
• Power Range in kW for controller
• Current rating (A)
• Country of origin
• Maximum DC Current (A)
• DC Voltage Range (V)

A comprehensive O&M manual, presented in both English and the local language, is essential for the SCS.

This manual must encompass information on various aspects, including solar energy and photovoltaic modules, DC/AC compressors and condensation, refrigeration units, tracking systems, as well as mounting structures, electronics, and switches.

Additionally, the manual should feature explicit instructions regarding the proper installation of PV modules, including do’s and don’ts, along with guidelines for regular maintenance and troubleshooting of the system.

The manual must include a helpline number and details about the service center. A warranty card for the modules is crucial.

The contractor is obligated to furnish a five-year comprehensive maintenance service for the solar cold storage system.

Only laboratories accredited by the National Accreditation Board for Testing and Calibration Laboratories (NABL) must undertake the testing procedures for SCS.

The SCS involves the calculation of six crucial parameters based on the measured test data.

These include the storage capacity of the thermal storage system (in KJ or kWh), minimum temperature attainable inside the cold room, efficiency of the thermal storage system, power requirement of auxiliary load efficiency of the solar charge controller, and the cooling rate (in °C per minute).

Recently, the Odisha Renewable Energy Development Agency (OREDA) issued an empanelment tender to commission 38 ten-metric-ton solar cold storage units.

Earlier, Uttar Pradesh invited bids for the design, supply, installation, and commissioning of 25 solar cold storage units on a turnkey basis.