Electricity + Control September 2019

ENERGY MANAGEMENT + ENVIRONMENTAL ENGINEERING

use of diverse power sources – solar or wind during the day, switching to other forms of generation such as biomass, or more conventional diesel generators, when the conditions for renewable energy generation are poor. Dall’Omo adds, “One of the most exciting aspects of a microgrid system is the potential for storing and exchanging power. For example, an office park that generates a lot of power during the day could pass on that stored power to a nearby residential community to be used at night. Depending on the setup, power generated by the community overnight could in turn be transferred back to the office park for use during the day.” While this would require a distribution network that could handle two-way traffic, Dall’Omo suggests that “… such relationships between business and communities could result in massive savings across the board and make huge leaps towards a cleaner energy environment in South Africa.” The challenges currently facing Africa’s energy sector are leading private businesses, residential communities, education institutions and others, to curtail their dependence on the traditional centralised model of power generation and linear distribution and to identify alternative, efficient power generation solutions. Siemens DES is designed to provide uninterrupted power and ensure a steady and reliable electricity supply to meet growing demand across the continent.

Facts & figures: DES, Siemens, Midrand - The office park covers an area of 22 351 m 2 and accommodates 800 to 1 000 workers daily. - The record shows 16 months of uninterrupted power. - Since the start of operations of the DES, the company has saved 2.4 GWh of electricity consumptionfromthenationalgrid:thatisabout 174 000 kWh per month, which represents 50% of the office park’s normal monthly consumption. - This also indicates a reduction of about 2 460 tonnes of CO 2 emissions to date. - While the average saving of 174 000 kWh per month represents exactly 50% of the company’s baseline monthly consumption; the past few months have shown closer to 60% less consumption from the national grid, due to system optimisation and battery usage. - The initial payback period calculated for the system was 11.1 years (including capex, financing, maintenance and a conservative estimate of power price inflation). - However, taking tariff increases and the actual DES generation figures into account, Siemens is confident that the full payback will be achievable within five years. - Overall project cost was R20 million, including refurbishments to the buildings, grounds and campus operations to improve built-in energy efficiencies.

Captured solar power is integrated into the microgrid controller, excess energy is stored in a 140 kWh battery, and the entire system is controlled via an IoT energy platform.

26 Electricity + Control

SEPTEMBER 2019