Carbon-Neutral Hybrid Solar Technology in Low-Rise Residential Homes

Carbon-Neutral Hybrid Solar Technology in Low-Rise Residential Homes

Carbon-neutral hybrid solar technology in low-rise residential homes: trends and drivers of residential solar energy usage in the East Coast of Australia.

The trend of renewable energy use in Australia to power residential buildings is evidenced by the clear rise in the installation of rooftop solar systems from 2016 to early 2017 and the continuous projection of high investment in the industry. Both case studies and surveys indicate that many families rely on the efficiency and stability of various residential energy storage systems to supply the electricity needed to their homes.

A thorough case study on residential battery storage, initiated by Ausnet Services in 2011, sought to examine the operation of ten hybrid energy systems of customers from diverse demographics to reveal data for cost-benefit analyses. All participants in the study had varying consumption levels of 7 kWh to 51kWh per day and were located in different distribution networks. The standard residential energy storage system under study was made up of a 6.6 kWhKokam lithium-ion battery, a Selectronic 3 kW inverter/charger, a programmable PLC controller, a communications system, and either a 1.2 kW or 3 kW solar PV system. The researchers then collected data at various points from each household as they went through five different operating modes of the storage system.

The storage systems were found to benefit the power network regarding peak demand management, wherein the battery systems were able to support the network during peak demand times and supplant the need for an upgrade in network capacity. Each customer’s contribution to the network peak demand was reduced by 1.1 kW up to 1.9 kW depending on the mode used by their battery systems. The likelihood of technical issues, such as voltage rise which could affect

surrounding customers, also went down due to the reduction of the amount of solar power exported to the power grid by the energy systems.

On the other hand, customers were better off using the energy storage systems to significantly reduce their electricity bills, with the reserve excess solar power combined with the use of off-peak power. The savings made by a customer under the most common solar PV tariff was around $342 per annum and around $3,500 over the whole lifetime of the system. However, the combined customer benefits and network benefits amounted to $6,800 which was far from the 2018 forecast of total cost at $10,700. The quantitative study instead referred to non-financial qualitative benefits of increased energy independence and backup power which could not be sufficiently ascertained but could make up the gap.

Reference to qualitative case studies may demonstrate how important the benefits above are. One such study, funded by the company Redflow Limited, focused on the use of two of its 10-kilowatt zinc-bromine hybrid flow batteries by Redflow CEO Simon Hackett in his Eastern Adelaide home starting early 2016. Aside from the Redflow batteries, the system was comprised of two 5000VA Victron Energy chargers, a 10-kilowatt peak solar panel array in four strings using two SMA 5000-TL solar inverters and a Victron Energy CCGX configured for solar self-consumption. The accompanying ZCell battery management system could also be managed remotely over the Internet from any compatible electronic device.Such a set-up allowed for his home to be powered solely by solar energy on a sunny week and for batteries to be recharged in the case of any outage.

In both normal and unusual conditions, Hackett attested to the consistently stellar performance of the energy system installed by Redflow partner Solar Depot. A surge of thunderstorms hit South Australia later that year in September, causing 

a nationwide power outage.[1] The Hackett family was able to experience the benefits of their battery technology seamlessly, as it was designed to activate automatically when the national power grid went down. As a testament to the reliability of the Redflow batteries, they learned of the electricity crisis in their area through social media instead of from their own experience.

            Another case study focusing on the McGarvie household, located on the coast in Eaglemont, Victoria, confirms how convenient it is to use installed hybrid batteries as a sure source of power. Mick and Maria McGarvie already grew food and harvested water naturally, with the next step in their self-sufficient lifestyle being the utilization of a hybrid solar energy system. In 2015, the couple installed sixteen Nerada gel-carbon batteries on the wall of their bungalow’s carport and 24PV ReneSola panels on their roof for their 6-kilowatt hybrid system, which also included a Selectronic battery inverter and a Kaco solar inverter.

            Despite the lower power of their hybrid system compared with the Hackett family’s 10-kilowatt system, the McGarviesmade similar findings with the Hackettswith regard to the daily recharging of the batteries via solar panels for nighttime energy use and the seamless take-over of the hybrid system upon power outage, which removed the need to reset flashing clock-radios. Furthermore, statistics from the local power company AGL Energy showed that the McGarviehome beat all energy-efficient homes in their neighborhood, with the McGarvies themselves reporting 90% solar self-sufficiency.

            Many conclusions can be made about the use of residential storage systems in Australia today. Firstly, the use of hybrid solar systems is highly reliable regardless of the variations in brands and specifications as well as energy consumption across 

a wide demographic of customers. These systems provide power on a daily basis to fuel the electricity demands of different types of households, whether it be a couple or an entire family. This is particularly important, as testified to by the Hackett study, in the event of natural disasters or other issues which may affect the power grid. The seamless nature of the transition from grid power to battery power is also a major advantage in the use of hybrid systems, as it allows for continuous household functions despite possible network problems.

Secondly, the benefit of self-sufficiency in energy is placed in high regard by many consumers, including those in the McGarvie study. The couple elaborated in that study that there is a sense of excitement and fulfillment in ensuring the stability of the household’s power supply. According to them, there is also more focus on switching off and saving batteries, which is an indicator of how energy conservation behavior is created.

            Thirdly, the use of residential batteries creates a more stable power network for the surrounding areas. High demand is offset by battery power, which reduces strain on the power network and lengthens the time before capacity upgrades are needed. In looking at the perspective of network operators, it is more sustainable to properly space out the refurbishment of a power network over a long period due to the massive expenditure required for upgrading capacity.

            Lastly, hybrid solar systems have been proven to reduce regular electricity bills by creating energy reserves for households to draw from in case of power outages or during periods of peak demand when electricity is costly. Concededly, the installation of these energy storage systems is costly, which the Ausnet study put at about $10,700 in the year 2011. The study itself notes that it remains to be seen whether the system costs may be reduced as technology costs may go down and the technology itself may become more refined to increase cost reduction. In fact, data from Solar Choice puts the average price of a 5-kilowatt solar system price

in Australia at $6,800, although costs may vary depending on geographical location, weather, temperature and solar feed-in tariffs among other things.

            All in all, the benefits of residential energy storage systems are numerous and for many people, worth the investment. While cost may be slightly pricey in the short-term, the reduction of electricity bills over a long-term period in addition to the benefit of energy conservation creates a strong case for hybrid solar systems in the general Australian populace.