All the way from Minnesota, USA to Chippendale . . .

All the way from Minnesota, USA, I have come to Sydney on a Study and Intern abroad program through my home university. Until the end of April of this year I will be interning with Michael Mobbs, and working on sustainable and off-grid projects.

•   Intern Jillian Meehan and Sydney Harbour bridge

Intern Jillian Meehan and Sydney Harbour bridge

As part of my internship, I am obtaining and analyzing data on the energy and water production and usage at Michael’s Sustainable House in Sydney.

The house’s batteries and solar panel system, which were installed by Michael Valantine’s company, MV Solar, are working smoothly and providing ample electricity for the family of five who live there – see Michael’s blog about the installation.

The only hiccup that has occurred was with the remote monitoring system, selectlive, which generates data for the solar panels. The system wasn’t collecting data on the solar panels’ performance.

To solve this, the faulty system was posted to the supplier to check, and they mailed back a replacement within a week. I was able to install the new system with little fuss. This installation by myself, with no electrical qualifications, demonstrates the user-friendly off-grid products MV Solar provides through their solar panel manufacturer, WINAICO

Since January 30th, the system has been producing data that I have been able to track using Selectronic’s portal. This portal allows users to track their solar panels’ energy production and energy usage as frequently as every hour. Users can view this data portrayed on an easy-to-read graph by selecting a particular day, week, month, or an entire year. 

• Screenshot of data

• Screenshot of data

Here is a screenshot from Michael’s remote monitoring online portal from displaying data from the week of February 3, 2019:

In this picture, I am holding my cursor over the bars that represent solar energy produced (yellow bar) and solar energy used (grey bar) on February 5 from 8:00 – 12:00, as you can see in the pop-up rectangle.

The X axis shows the dates on which the data was collected and the Y axis shows the amount of energy produced (“Solar”) and energy used (“Load”) in kWh. Again, a user can change the view of the graph by, for example, electing to look at just a single day—this would present data for each individual hour of that day, as opposed to sets of four hours which are displayed in the Week view.

What does the data tell us about the actual performance of the batteries and solar panels?

Using the portal, I was able to obtain data whilst off the site from every hour of every day since I installed the new remote monitoring system at Sydney’s Sustainable House.

By recording the amount of energy in kWh produced and used for those hours, it was possible to calculate the averages for each day. This enabled me to create the following trend graph showing the average hourly solar energy produced and average hourly solar energy used from January 31 through February 11.

• Solar panels - average hourly energy production and use

• Solar panels - average hourly energy production and use

Overall, the production of energy typically exceeds the usage. This is what you would want for your solar panel system because you wouldn’t want to be using up more energy than you actually have. But, as you can see on February 1, this very issue occurred. Luckily for the family living in the house, there are batteries that store extra energy for rainy days and nights.

So, how many days of rain can the system withstand before running out of solar energy?

The entire battery holds up to 19.2 kWh and rarely is more than a fraction of a percent away from this maximum amount at all times.

By calculating the average amount of energy the house uses in a given day, we can figure out approximately how many days the battery can last without sun (so, without solar energy being used directly). The average daily energy consumption for the house is 6.82 kWh, therefore, the battery can last just under three days without receiving any energy from the solar panels.

This is a very unlikely scenario considering even days that do get a lot of rain still receive some amount of sunlight which can be used as energy or stored in the batteries for later use.

How does the system actually work?

First off, this system is designed and operated to be fully off-grid, meaning the house generates and uses its own energy—and does not need to rely on the city grid network.

Some solar panels collect available solar radiation directly from the sun at any given time and throughout the day. In other words, direct available sunlight is collected by the solar panels and used by the house for its energy needs. 

Other solar panels also collect energy directly from the sun but send this collected energy to the house’s batteries instead of directly to the house’s energy needs.

So, at any given time, both the batteries and direct sunlight from the solar panels will supply the house with the energy it requires—again, this depends on how much sunlight there is on a given day (a rainy day will use more energy from the batteries due to lack of sunlight).

If all energy usage demands have been met for a day and there is excess solar energy still available, then this excess energy will first be sent to charge the batteries if they are not fully charged. However, if the batteries are fully charged, the system’s controllers will reduce the solar energy input to what is required by the load—the house’s energy usage—and only a small amount will be sent to the batteries. Any potential excess solar energy will not be used.

This system also has the capacity to connect to the city’s grid network. If a user decided to connect to the grid network, one reason would simply be to send any excess solar energy to the grid and receive a small payment from the energy company. Another reason would include the opportunity to connect the system with neighbouring solar panel systems (they do not have to be this exact system, just something similar) in order to charge their batteries or supply their energy needs when required.

The system components include:

·      Re-wire and reconfigure existing solar panels

·      New control panel, cabling and electrical protection

·      New 6 x 270 watt multi-crystalline solar panels

·      2 regulators (60 Amp MPPT Morningstar)

·      Selectronic SPMC 241, 24v 3kW inverter SP Pro

·      Morningstar Tristar Digital Meter (TS-M-2)

·      Fronius Primo 3kW AC coupled inverter (Selectronic Certified)

·       12 x 2V Gel batteries 800AH Neuton Gel Flat Plate

·      Removal of 6 maximisers and Tigo management system from existing six panels

·      Removal of failed Alpha-ess battery storage system

 With a couple of months left in my internship to review the growing amount of data from the system, and with my direct experience having a five-person household contributing to that data, I expect to return to the United States with a basic yet valuable understanding of how an off-grid energy system can work in the heart of such a modern city like Sydney.

As a current sociology major, prospective lawyer, and life-long advocate for the environment, I couldn’t have found a better internship position than with Michael, a former environmental lawyer himself. By handling material with which I have very little previous knowledge or experience working with, I am constantly gaining new skills that I otherwise would not have the chance to develop during my day-to-day sociology studies. My experience here is further enhanced by the fact that I know I am, in some way or another, helping the environment and spreading knowledge so that others may do the same.

Jillian Meehan