Nick Jones, Aztec Solar Energy’s project manager, spoke with REI about the need for proper planning to minimise disruption on a busy campus and ensure the systems’ long life.
In common with many educational establishments, the University of Warwick is committed to reducing its carbon as part of its net zero pledge. Its ambitious plans aim for net zero carbon emissions from energy by 2030 (scope 1 + 2). To help it meet this goal, Aztec Solar designed and installed solar PV systems on the rooves of six of its buildings. Phase 2 will see further rooftop solar installations later in the year.
The current installation is expected to generate 511.32MWh per year and save 99.62 tonnes of carbon. This is the equivalent of 4559 trees and will save the university 128,000 per annum from its electricity bill, giving a payback on the investment in just 6 years.
The commitment makes sense not only for the university’s ambitious carbon targets but at a time of rising energy costs; it will help reduce its future expenditure.
Minimising disruption
Installing six large PV systems is a big commitment, and at a busy university with 29,000 students plus staff and members of the public on-site, both health and safety and minimising disruption were vital factors, particularly during cranage and scaffolding work to get the PV panels and supporting structures onto the rooves.
It was a complex task for a number of reasons. The designs for each building were extremely detailed and had to account for different roof types and their load-bearing capacity. In addition, Aztec Solar had to manage multiple teams on buildings with different specifications and installation requirements. Some of the buildings were very big and needed tall cranes for lifting, which required close coordination with the facilities team to get work permits.
All of this work needed to be completed without disturbing staff and students. This meant that most of the lifts, scaffold erections, and electrical shutdowns to connect the PV system to the supply were done at night. For one building, contractors were on site at 4:00 a.m., and because the project included six buildings all completed in just nine months, there was also a separate secure on-site compound for storage.
Design and specification
At Aztec Solar we always plan ahead on an installation. After an expected payback of about six years, each of these systems will save the university money from its electrical supply and help it meet its net zero pledges over the long term.
A good PV module will still be producing 90% of its output even after 25 years, so the system’s potential lifespan is often longer than you think. This makes the system’s design crucial both in selecting the right products and planning for its lifespan.
In its drive for a more sustainable future, the university was keen to ensure the best solution. This meant that we had to specify tier-1 products and account for their embedded carbon. Tier 1 products mean that Bloomberg has independently audited them for both electrical output and provenance, so there was no labour exploitation involved in their manufacture.
We agreed on using more than 1,400 Eurener 450W all-black panels for the six buildings. Manufactured in the EU, these panels have lower embedded carbon than many other panels. They are efficient and reliable panels built to last and have a good output even at lower light levels, such as on a cloudy day or during dawn and sunset.
Future maintenance
We also needed to ensure ongoing efficient production and the safety of maintenance personnel and emergency services, such as firefighters, who may need access to the roofs during the systems’ life.
Solar panels will continue generating electricity even in cloudy weather and typically have an output voltage of 47V. Connecting these together in a string creates a high voltage of up to 1000VDC+ on a big installation, which can be dangerous to maintenance or emergency personnel. Traditional string inverters cannot reduce this DC voltage even if they are turned off.
Fortunately, modern inverter technology, like the SolarEdge system that we used at Warwick University, has power optimisers and individual monitoring on each PV module. This allows the automatic shutdown of PV arrays and lowers and maintains the voltage in all DC conductors below 50V and to 1V per optimiser for either maintenance or in an emergency. The inverters are also integrated with the fire systems with emergency stop buttons for safety.
A further safety requirement for inverters is that they must detect and terminate an electrical arc by shutting it down. Such arcs could be caused by damaged connectors or cables or improper connection.
This technology also keeps the university’s output levels high. In a traditional arrangement, if one module is not working properly, then other modules in that string will drop to a minimum level. With the SolarEdge technology, if one module is not at full capacity for whatever reason, it does not affect the other panels’ output.
The installation at the University of Warwick also provides fire-fighter breaks between panels for access in an emergency and for future maintenance, whether cleaning, repair, or replacement.
Monitoring
Ongoing operations and maintenance over the systems’ life are vital to maximise renewable generation. While PV panels will last well in excess of 25 years, inverters could need replacing after 10 years. It means that we had to plan for future access for the maintenance of both and their potential replacement.
With 1900 PV panels already installed and with plans to install several thousand more at the university, we connected the systems up to monitor ongoing production to see what each of the six systems is producing and to detect and accurately locate faults
This is a vital consideration during the installation with a clear plan of what is installed where so that fault finding is fast and efficient and it’s safe and easy for the team to take remedial action – whether it’s for something as simple as cleaning the PV panels or to replace equipment.
With phase 1 at the university now complete, phase 2 is due to start this year when up to 14 more buildings will have PV systems installed on their roofs.
The University of Warwick was a huge PV installation that required detailed plans and ongoing coordination to minimise disruption and ensure safety. But beyond that, we need to remember that such installations will last decades, and you must plan for future maintenance, repair and replacement.
When you install it properly, a solar PV installation will generate renewable energy over a long life, help organisations meet their zero carbon pledges and reduce their ongoing running costs.
Images: Aztec Solar