Best Environmental Impact 2021

Winner: Re/volve Energy for the Cohaus Project

Cohaus is a community of people designing and financing their own twenty-unit housing development in Grey Lynn, Auckland. Their vision was to build affordable housing that uses smart design and innovative technology to create a community where it’s easy to live comfortably while minimising resource use.

Re/volve Energy has worked with Cohaus over the past two years to design and implement a shared energy system. The system allows the residents to leverage the cost effectiveness of centralised energy systems to reduce capital and operations costs, and CO2 emissions. 

The system consists of the following components:

Re/volve worked with the architect to specify a 40kWp roof mounted system. The system feeds all the apartments via a consumer network. Electricity exports are to be minimised as electricity will be used in the apartments, hot water heat pumps, and EV chargers ahead before it is exported via the gate meter. Demand will be actively managed in the key systems, see below.

The photovoltaic system was supplied by Superpower.

Central hot water
Re/volve Energy worked with the architect to study the feasibility of a central hot water heat pump system. The additional capital cost of the heat pump system was paid back through energy savings in less than 3 years ($15,000 of operational savings per year, increasing over time). In addition over 20m² of floor area was saved in the apartments by avoiding the installation of individual hot water cylinders, with a value of $100,000.

The hot water heating system was supplied by Collins Heating and Gas.

EV charging
Cohaus will eventually have 6 shared electric vehicles, building on the 2 that are now operating.

Re/volve Energy has supplied EV chargers that integrate with the demand control system. This will allow EV charging to be reduced or curtailed during times of peak demand and for charging costs to be reduced by maximising charging at times of excess PV generation or low electricity pricing.

Demand control
Re/volve Energy has designed and supplied a load control solution that manages the key loads at the site including hot water heating, EV chargers & space heating. Load control operates to reduce operational cost by maximising the use of onsite generation and using lower cost off peak electricity.

Demand control has allowed the site to avoid the additional capital costs of an on site transformer (estimated as a saving of ~$40,000) by reducing the grid connection by 30%, down from 250A to 180A. This has also reduced operational costs by around $750/annum.

The site uses a consumer network with a single grid connection to supply electricity to the 20 units. Cold water is similarly distributed to apartments from a single watercare connection, and hot water via a ring main from the central hot water plant.

Re/volve Energy has supplied our data acquisition, metering & billing solution to the site in order to ensure that the operational and capital costs of the system are recovered fairly from the residents. The system:

  1. Records the metered electricity, hot water and cold water use of each apartment.
  2. Stores all the data in the cloud.
  3. Stores and manages tariffs for the service centrally. Including time of use tariffs for any service.
  4. Automatically generates invoices monthly for the services which are pushed into Xero where they are managed and payment collected. 
  5. Allows the use of solar PV generation by apartment to be determined on a half hourly basis and billed at a separate rate to grid electricity to incentivise residents to change their usage patterns.

Monitoring and visualisation
The same data that has been captured for billing, plus data from additional check meters which measure central loads (e.g. laundry, heat pumps, PV & EVs) can be visualised centrally. A fully customisable dashboard allows the managers of the site to keep track of consumption, and generation of electricity, heat and cold water. 

A simplified dashboard will be shared with residents to allow them to understand the best time to use electricity & hot water

The system also tracks costs and savings in real time to allow live reporting of cost and carbon savings.



More about Revolve Energy


Runner-up: Sunergy Solar Ltd for the Stewart Island Solar Project

"Sunergy Solar travelled to Stewart Island in April 2021 to install an 18.9kW array, Fronius SYMO 5 and SYMO 10kW GEN24 inverters and an 11.04kWH BYD HVM battery. This project was funded through the Ministry of Educations Sustainability Contestable Fund.

Logistically the project was challenging as we are based in North Canterbury and we had to tie in with the roofing contractors who were Invercargill based. Post Covid the Island is incredibly popular so we had to book travel and accommodation well in advance. We were not aware that April is known as the poorest weather of the year for Stewart Island, so hardly the ideal time to replace a roof and install a solar system. Both the roofing contractors and our team put in an awesome effort to ensure we were finished by the end of the school holidays.

Power on Stewart Island is generated via 5 diesel generators and the current cost of electricity for the residents is 62c/kWh. There is a perception both locally and nationally that Stewart Island has terrible weather and would not be suitable for solar. As you will see in our attached documents, since its commissioning at the end of April, our system has generated more kWh than the school has consumed.

From an environmental perspective, the solar system on Halfmoon Bay School is projected to generate 21,150kWh per annum, which, based on the current diesel consumption for the islands power supply, should save about 3000L of diesel and approximately 7500kG (7.5t) of CO2 emissions annually. If the solar system performs as expected, or better, it is entirely possible that solar could be considered a viable option for Stewart Island to reduce its diesel consumption and CO2 emissions. Additionally there would likely be a long term reduction in the cost of electricity for the islands residents. Sunergy Solar ae incredibly proud to have been involved in this project, we are excited to watch the systems performance over the next year and hopefully be a part of the energy transformation of Stewart Island.

More about Sunergy Solar

Tell us what you think

Or sign in with email
  • Validation errors will appear here if any occur.
Please check your e-mail for a link to activate your account.