DC Electricity Generation Plant on your Roof !

Solar PV design and installation is regulated by numerous standards, guidelines and instructions.

These are required to be followed to ensure that systems are durable; components' warranties remain intact (e.g. modules, inverters, racking, switches, connectors, cable, etc.) and most importantly the systems are safe from risks of fire, and users protected from electrocution, etc.

 

The Dangers

Most solar PV systems run at Voltages at or near 600 and often higher (upto 1000V). These are dangerous levels and present significant risks to sites including electrocution and fire.

In addition, Solar PV cannot be just turned off. A solar panel will keep generating energy as long as there are photons!

To quote AS5033... 'Direct Current systems, and photovoltaic arrays in particular, pose hazards in addition to those derived from conventional a.c. power systems...'

 

Obvious deviations from standards

There are numerous aspects in which a system must meet the standards. This page is not an exhaustive one but endeavours to capture some important examples:

- Installation of the roof-top solar p.v. isolator directly on to the solar module. This usually results in a loss of warranty of the module.

- Improper sealing of the roof-top solar p.v. isolator. Every isolator comes with specific ingress protection ratings (e.g. IP65 or IP67). These must be maintained. Any holes and or penetrations made into the isolator must be made in a manner that maintains the original IP rating. Silicon or open-ended conduits do not maintain the rating. This is specific to both AS5033 and AS3000.

- Incorrect or lack of torqueing of the electrical connections. A common cause of fire in the roof-top d.c. isolators is arcing due to loose terminals and the resulting runaway thermal reaction. It is always recommended that the cables should be put in boot-lace ferrules and the screws torqued to the correct rating as prescribed by the manufacturer. Too loose and arcing will occur; too tight and the threads will strip out, the screw may have been stretched too much and will come loose with the same result.

- Modules' mid and end clamps over or under torqued. This can result in damage to the frame of the module with the result that moisture may penetrate the module and or the cells may be damaged.

- Use of impact drivers/rattle guns on the clamps attaching the modules to the frames resulting in possible cracks to the cells which may develop into hot spots over time.

- Improper earthing of the modules with the result of potential electrical hazards being present on the roof.

Why do deviations occur?

Given that the standards are so clear, manufacturer's instruction available, systems having to be installed by accredited installers/electricians and the installation then being subjected to an 'independent' audit, why the deviations? Why the anomalies? Why the fires?

1. The principal reason is the lack of enforcement of the regulations. The industry is managed by the CER (Clean Energy Regulator, which is a government body); however the CER, a body that conducts technical-compliance audits on actual installations, does so to a limited level - both in terms of sampling and the extent of checks; the CER leaves the regulation of the industry to the CEC (Clean Energy Council) and the relevant state energy authorities.

2. CEC is an industry body funded by installers and manufacturers (it is NOT a government body). The CEC tries to manage accredited installers' adherence to standards using a points' demerit system. If an installer is found not to have followed the standards, etc. then depending upon the gravity of the deviation, that installer may suffer some penalties in the form of points lost, suspension, etc.

3. The inspection. Every system must be inspected by an 'independent' inspector. In almost all cases, the solar p.v. installer who has installed the system hires the inspector and is responsible for meeting the inspector's costs. Further, it is common to find that installers have long-standing working relationships with a select inspector or company of inspectors.

4. The inspector's brief is very narrow. It does not cover the whole of the installation. The inspector charges a nominal fee (typically under 1% of the value of the install, less on large systems).

5. What about ISO certifications, does that guarantee quality? No. ISO certification is simply a process of attempting to ensure that the relevant industry standards and quality-control procedures are followed. IT DOES NOT PROVIDE ASSURANCE THAT INDEED THEY ARE. ISO Certifying inspectors have no specialist knowledge of the industry.

6. What about the CEC retailer code of practice? This code is an attempt to ensure solar retailers provide certain basic guarantees and assurances, e.g. 5 years' of workmanship guarantees etc. It is NOT an assurance of quality of installation, workmanship, etc.

What recourse does the customer have?

As at the time of this update, the CER have advised that the State Energy Regulator is the correct port of call.

 

 

 

 

The Standards

The main standards regulating solar p.v. design and installation in Australia are:

- AS5033

- AS4777.1, .2, .3

- AS3000

- 1170 - Wind Actions

These standards are very specific, spelling out mandatory requirements which 'shall' be followed and recommendations which 'should' be followed.

 

Guidelines and Manufacturers' instructions.

A solar PV system is made up of numerous components all of which are put together at site, often on a roof.

Every manufacturer has specific instructions for the installation of its products. Failure to observe these instructions will compromise the safety of the site and also often lead to loss of warranty.

Take the panels for instance. For the full warranty to be maintained the panel must be mounted such that the supporting rails are withing 1/4 and 1/8 the length of the module. This applies to most panel manufacturers.

Every solar system will require d.c. connections to be made under the modules. When new connections are made (over and above those already on the modules) new connectors have to be installed. A common connector is the MC4 made in Germany. MC4 has strict instructions of how these connectors should be installed including the use of approved tools. Warranties are only maintained if these instructions are strictly followed and the correct (approved) tools used. More importantly, safety is maintained and the risk of arcing avoided.

All cable manufacturers have strict requirements covering bending radius that must be followed for the warranty to remain. While difficult at times, in most cases it is possible to maintain this radius and minimise the risk of a failure of the cable's insulation material.

Solar P.V framing systems (commonly knows as 'racking') must also be installed strictly in accordance with the specifications to ensure the requirements of AS1170 are met. This includes the correct torqueing of all fastners, maintaining the correct spans, and cantilevers, ensuring that the spacing of the feet is appropriate for the height of the building, location on roof and categorisation of the building, etc.

It is common to find that impact drivers are used for fixing the framing. Impact drivers can deliver high torques, well in excess of the tolerance levels of the fastners used, almost always ending up in a compromise of the fastners.

Commissioning & Testing: Every solar p.v. installation must be subjected to a certain minimum set of tests and these must be documented and provided to the customer.

Insulation Resistance Testing: This is an example of one of the mandatory tests as required under AS5033. It ensures that the cables are safe and have not been damaged, and that the general insulation of the whole installation is safe. It requires specialist insulation-resistance test equipment (note, the standard Fluke insulation resistance test meter does not comply unless steps have been taken to short circuit the p.v. circuit before carrying out the test).

Performance tests: Another example is the requirement to monitor the current output of the system and factor in the irradiance at the time. To do this correctly an irradiance meter must be used, held up against the light and the irradiance measured and recorded. If, for instance the current of a system should be about 8Amps under light of 1000W/m^2 (i.e. a nice bright day) then if the light is 200W/m^2 the current will be proportionately lower.

Labelling: Most customers are unaware that there are strict standards covering the durability and legibility of labels. For instance, did you know that all labels on the roof are required to be 'sufficiently durable for purpose'? This means that a Dynalabeller or a simple sticker does not comply.

Documentation: All p.v. systems must be supplied with complete documentation including:

1. Single line diagrams

2. Testing & Commissioning checklists

3. Maintenance regime with recommendations and a log

4. Instructions for action in the event of an earth-fault alarm

5. Expected yield

6. Technical specifications of the modules, inverter, isolators, cable, monitoring devices, and racking

7. Certification of the racking

8. A list of all equipment supplied

9. The shutdown and isolatoion procedure for emergency and maintenance

10. Installer's declaration

Disclaimer

This section is not exhaustive. For a full understanding of the requirements it is recommended that professional advice be obtained.

 

 

 

 

Best Practice / Research

In addition to standards, guidelines and manufacturers' instructions, iEnergytech has developed unique best practices based (partly) on our own in-house research.

Should we torque correctly? Do all DC isolators have the same series' resistance?

Photo of a 10kWp solar pv installation

Contact-resistance tests of DC isolators using a Megger milliohm meter revealed the importance of correctly torqueing electrical screws.

Photo of a 10kWp solar pv installation

And not all isolators were found to have the same levels of internal resistance. Some were low, others high, with some fluctuating wildly!

 

Electro-magnetic Radiation

In 2010 iEnergytech conducted several tests to establish the strength of the electro-magnetic field of an inverter under operating conditions; the knowledge gained from these tests is used when locating inverters in sensitive areas or homes.

 

Inverters and RF noise

RF noise can be disruptive to HF comms' systems. In 2011 several tests were carried out on a range of inverters to establish which were the RF noisiest.

Photo of a 10kWp solar pv installation

Tests covered SMA, Latronics, Diehl Ako and KACO inverters.

 

Photo of a 10kWp solar pv installation

A spectrum analyzer was used together with an inductive-loop sensor.

The peak on the left-hand side reveals "noise" at that frequency. Important considerations when locating and selecting the "right" inverter.

 

 

Are those cells working properly?

IR images can reveal things invisible to the naked eye, like these hot cells pointing to possibly damaged diodes and...potentially lost yield.

IV curve of a panel with a damaged cell

 

Damage to cells during transport and installation:

IV curve of a panel with a damaged cell

Damage during the transport and installation phases is common. Testing the modules prior to final commissioning can reveal such damaged cells, saving significant losses in yield.

 

 

 

 


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