Solar Power | Botany Cope

Botany Cope
  • 30 residential lots
  • 4 commercial lots
  • 4 residential levels
  • 1 commercial level
  • 1 parking level
  • 2 lifts
  • 2 buildings separated by an internal courtyard
  • completed in 2003

Botany Cope installed a 4.9 kW solar system that is meeting 23% of its common property electricity demand

Download a case study published by the City of Sydney

Background

An energy audit in 2013 advised that a 15 kW system would be the "right size" for a solar array, based on the scheme’s common property energy consumption and demand profile at the time.

After implementing the "low hanging fruit" recommendations from the energy audit, mostly lighting projects, electricity usage dropped by 49% in 2 years.

Graph of Monthly Energy Consumption

49% reduction in energy consumption over 2 years from energy efficiency projects

Subsequent analysis of energy demand revealed that only a 5 kW system was needed.

Complete your major energy efficient projects first so you don’t need to outlay for a larger system than really necessary.

Approvals

At the November 2013 AGM owners unanimously voted to install a 15 kW solar array and the executive committee was empowered to spend up to $24,000 on the project. Owners agreed that it was important to “future proof” the building as well as save on costs in the longer-term.

A subcommittee was formed to manage the solar installation.

It was not installed until July 2015.

Site layout

Overshadowing at sunrise from neighbouring building

Overshadowing at sunrise from neighbouring building

Botany Cope comprises two separate buildings, each on a different street frontage, with a common courtyard between them.

A tall building on its northern boundary casts significant shadows at different times of the day.

There was too much overshadowing of the building on the western side of the property, so only the rooftop of the eastern building was considered.

Supplier selection

9 companies were initially approached to quote on the job.

Several suppliers proved to be unreliable and non-responsive.

Four companies submitted proposals after site visits and many conversations and meetings with the subcommittee to understand the options available and installation issues unique to the site.

Two suppliers were actually paid a deposit on the work at different stages, but both returned the deposits once their installers determined that the configurations quoted by their sales people wouldn’t do the job!

The project was stalled until a new company was recommended to the sub-committee. It proved to be the most professional of all, with an extremely competent and reliable. He had the knowledge and equipment to assess every aspect of the job, including the shadowing impacts from the neighbouring building, and was accredited with the Clean Energy Council. The sub-committee proceeded after checking references, warranties and previous projects. A case of saving the best until last…

Options considered

Most quotations were similar with 180 to 220 W per panel

Micro-inverters were an attractive option, because only individual panels and not the whole array would be affected by overshadowing. The final design worked around this issue without the additional cost of micro-inverters

Installation considerations

Solar inverter installed in electrical cupboard

Solar inverter installed in electrical cupboard

After checking with the Council, there was no need for a Development Application. The angle of the solar panels’ projection from the almost flat roof would not exceed 0.5m, which meant it met Council’s guidelines for Exempt Development.

Rooftop maintenance items (e.g. flashing) were attended to before the array was installed.

The roof is corrugated iron, and all mounting screws have a rubber seal. The roof was inspected for leaks after the first heavy downfall post-installation.

Access to the roof was one of the trickiest issues, as the panels didn’t fit through the roof access manhole. One of the penthouse owners kindly allowed her balcony to be used as a staging point for lifting the panels to the roof.

The inverter needs to be close to the panels. Access issues prevented it being installed in the roof space. Luckily there was enough space for the inverter in an electrical cupboard on the top (4th) floor, almost directly below the panels, that facilitated connecting the inverter to a power box on the floor below (3rd floor). A fan was installed in the cupboard, venting heat to the roof space.

The array was sized so that the electricity generated would be slightly less than that needed, to ensure that nothing was being sold back to the grid. The return on selling back to the grid is very poor (6-8 cents per kWh, and there are potential taxation issues for the owners)

System Configuration

Solar panel array on rooftop

Installed solar panel array

4.91 kW system comprising:

  • 15 x SunPower 327W panels
  • 1 x SMA 5kW TriPower (3 phase) inverter

The panels used have a higher capacity than others proposed (327 W versus 180-220W), reducing the number of panels needed. The smaller system then allowed better positioning of the panels to maximise sun exposure and avoid shading as much as possible from the taller building next door and the exhaust vents on the roof.

The system will generate approx. 21 kWh per day on a yearly average and the available annual sun is calculated to be 87%.

Solar switch on main switchboard

Solar switch on main switchboard

Sign on door to main switch room

Sign on door to main switch room

 

Cost

The total cost of the solar system was $14,086 ex GST

This included a discount of $3,636 for 101 Small-scale Technology Certificates (STCs)

50% of the cost ($7,000) was funded through an Innovation Grant from the City of Sydney Council.

Outcomes

The solar array was installed in early August 2015. In the 4 month period from September to December 2015) it:

  • saved 3,357 kWh
  • reduced electricity usage by 23.5%
  • reduced electricity costs by approx. $700 (ex GST)

The payback period is approx. 3.3 years when the grant is factored in, and 6.7 years when the grant is excluded from calculations.

The following figure shows the decline in energy consumption compared to the same period the previous year.

Graph showing decrease in energy consumption before and after solar installation

Solar Savings

The following load profiles compare a week in September 2014 and a week in September 2015 after the installation of the solar array. They show consumption in 30—minute intervals across the 24 hours in each day.

2 graphs showing deman profiles for the same week in 2014 an 2015

Comparing demand profiles for a week in September 2014 with the same week in September 2015

Occasionally the output of the solar array is greater than the demand from common property and electricity is exported to the grid. The solar array only exported 41 kWh in the 4-month period. This equates to an export ratio less than 2%, indicating that the solar array is suitably sized.

The following load profiles show site electricity usage and electricity export for one week in November 2015.

Load profiles showing electricity exported and electricity used fom the grid for one week in November 2015

Exported electricity & Electricity used from the grid

In addition to the financial savings, the community is feeling happy to be “green”.

Graphs of energy consumption before and after the installation were posted on the noticeboard.

Last Updated: 
Tue 12/04/2016

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