Reducing grid reliance to reduce costs

With loadshedding impacting on productivity and income generation, and increasing safety and security risks, investing in solar photovoltaic (PV) has become more common. Consequently, getting a thorough electrical usage and needs analysis done to determine the best system design is a need that renewable-energy franchise One Energy Group helps companies meet, providing guidance to ensure that they receive a favourable return on their solar investment.

“The proper monitoring and analysis of electricity usage will reveal when the peak electricity demand happens and how much is used on a variety of circuits,” One Energy Group marketing director Teresa Settas explains.

She notes that after monitoring consumption it is possible to design a system that will use as little as possible from the grid, while enabling the implementation of energy saving measures to ensure that the property is as efficient as possible.

Effective monitoring also indicates which appliances or devices are pulling the biggest electricity loads, thereby allowing clients to reconsider the time and duration of using certain appliances.

Settas cautions that the installation of an inverter and battery backup system without solar generation capacity means that the grid will recharge the backup system, which increases electrical costs; the addition of solar panels will enable self-generation, thereby reducing costs.

She explains that for many businesses that operate during the “daylight hours” the addition of solar panels for self-generation would be able to supply the bulk of their electrical needs, suggesting that when selecting panels, it is better to invest in higher grade monocrystalline panels, if it is economically viable.

Settas points out that, should the solar array be producing excess energy, there are certain municipalities that will have net metering, allowing for the excess to be fed back into the grid, though this requires a costly upgrade to the meter.

She suggests adding battery storage instead to store excess energy, not only for when the grid goes down, but also to reduce grid usage as far as possible, to avoid the increasing costs of grid electricity.

Further, she advises that the inverter should first divert power to the property and any other connected circuits before charging the batteries again.

She adds that one of the key issues with cheaper, “off-grid” inverters is that many are unidirectional, resulting in the solar power only addressing the essential services circuits, and savings being unable to be made on the higher load items that are not backup side of the distribution board.

The more “sophisticated” hybrid inverters, meanwhile, are bidirectional, allowing savings both upstream and downstream of the inverter, drawing power from both the grid and battery storage in a coordinated manner, thereby increasing the use of self-generation and decreasing reliance on the grid.

“Every kWh of solar electricity generated is another knocked off your electricity bill,” comments Settas.

Lithium Battery Lifetime Cost

“There is a perception that lithium-ion phosphate batteries installed as a key component of a hybrid PV system are very expensive. This is simply not true if one calculates the average cost per kW over the life of the battery,” explains Settas.

She elaborates that when compared with other sources, the battery energy cost is significantly lower than the cost per kW from State-owned power utility Eskom or from the local council, as well as compared to costs per kW accrued using diesel generator.

She emphasises that diesel generator sets run at a high average cost of between R6/kWh and R8/kWh, and also need regular maintenance, which exacerbates the costs.

She notes that a company’s strategy should be to cycle the lithium batteries and maximise the installed inverter and panel array capacity to ensure the system is providing as much as possible of the client’s daily electricity consumption.