Quality Assurance

To assure a minimum quality of a SWHS, the collector should be tested and certified and the SWHS well documented. It is recommended, that the system integrator (supplier) of the SWHS provides following documents to the customer.

Solar thermal collectors and SWHS certificates

A solar collector test certificate, issued by an accredited test institute, should be provided by the manufacturer. It could be either a certificate according the global standard ISO 9806:2013 or according the Indian standard IS 12933:2003 for flat plate collectors (FPC) or IS 16543:2016 for evacuated tube collectors (ETC).

If a factory-made SWHS system is used, which is usually only the case for small domestic hot water systems for residential homes, certificates according IS 12976:1990 for FPC systems or IS 16544:2016 for ETC systems should be provided.

SWHS documentation

Following documentation should be provided with each SWHS:

  1. A list of parts with quantity and key data (e.g. size of collector area, volume of storage tank, thickness of tank insulation, etc.).
  2. A hydraulic scheme showing how the components are connected and how the fluid is flowing through the system (with references to the components listed).
  3. An operation manual, explaining, how the SWHS should be operated, including:
    • if manually operated: description, when the operator shall switch on and off the pumps and what he should take into account
    • if automatically operated: description, which parameters should be set at which value (e.g. what should be the temperature difference between the collector and the storage to start the pump).

    Further it should be described, how the operator can check, if the SWHS is operating well.

  4. A forecast of expected energy yield from the SWHS, this means, how much solar energy will be delivered to the process (point of use) per year and how much fuel is expected to be saved per year under typical conditions.
Hydraulic schemes of the collector field and the solar system of the HP Dairy plant

Basic Monitoring

To evaluate, that the SWHS performes well, it is recommended to do some basic monitoring.

By installing temperature sensors in the collector field (at the outlet of one collector) and the storage tank (at different heights) it can be controlled, if the SWHS is operating as expected, e.g. the collector temperature should reach a minimum temperature at sunny days depending on the efficiency and the type of operation (e.g. 70 C) and the storage temperature should increase in the upper, the middle and at the lower part of the storage tank, if the storage is charged during day and the heat is not consumed immediately.

By installing a heat meter between the SWHS storage tank and the connection point to the process water system, it can be controlled how much energy (how many kWh) is delivered to the process. The monthly or the annually delivered amount of energy can be compared with the expected solar yield. To calculate the energy content of the saved fuels, the solar energy delivered must be divided by the efficiency of the boiler.

Electronic temperature sensors (left) with temperature display and thermometer (right)