Hendrik van Huyssteen, MD of Energas, talks about the variety of fuel gases available in Africa and their potential use to power Energin CHP gas engines as an energy-efficient and cost-effective alternative in cities where grid-connected power infrastructure is contrained.
Property developers are experiencing increasing constraints with regard to the availability of reliable electrical supplies for new developments. The population density in many expanding cities is resulting in a growing lack of adequate electricity supply infrastructure. Developers are buying houses on large properties and converting them into high-density, multi-storey dwellings. There are not enough transformers and cables available to supply these developments with sufficient electrical power.
There are cost-effective solutions, however. Electricity can be generated efficiently by gas-powered generators. The cost of gas is generally much lower than diesel and various gas options are now available.
- Piped natural gas: In Johannesburg, the East Rand and Centurion, natural gas pipelines are available in many areas. A methane-rich gas pipeline runs from Secunda to Witbank, down to Durban and from Durban up to Richards Bay and piped gas is available from Sasol, Egoli Gas and Novo Gas.
- Compressed Natural Gas (CNG): CNG is natural gas compressed into bottles at up to 250 bar. It is available from suppliers in KZN, Johannesburg, the East Rand and Witbank. CNG can be delivered in a radius of 200 to 300 km from the base station. The cost of CNG is generally higher than piped gas as it has to be compressed into bottles, transported and then pressure reduced at the end-user facility.
- Liquified petroleum gas (LPG): LPG is a mixture of butane and propane and has a high energy content. It is retailed in bottles up to 48 kg but is also available in larger volumes in underground or above-ground tanks. LPG is generally more expensive in Rand per Gigajoule than piped gas and CNG.
- Liquified natural gas (LNG): LNG is abundantly available on the world market and used in large volumes, but is not yet available in South Africa. LNG is natural gas that is cooled down to very low (cryogenic) temperatures so that the gas becomes liquid. LNG has a higher energy density than CNG and is generally priced higher due to the cost of cooling and regasifying. An LNG plant is going to be built in northern Mozambique to deliver LNG by 2024.
- Biogas: Biogas is a biofuel that is naturally produced from the decomposition of organic waste. When organic matter, such as food scraps and animal waste, break down in an anaerobic (oxygen free) environment it releases a blend of gases, primarily methane and carbon dioxide. Biogas is produced at various plants in South Africa. It can be used to fuel gas generators.
- Woodgas: Wood gas is a syngas fuel that can be used in furnaces, stoves and vehicles in place of gasoline, diesel or other fuels. During the production process biomass or other carbon-containing materials are gasified in the anaerobic environment to produce hydrogen and carbon monoxide. These gases can then be burnt as a fuel within an oxygen-rich (aerobic) environment to produce carbon dioxide, water and heat.
Energin combined heat and power (CHP) gas engines
All the above-mentioned gases can be used to fuel Energin gas engines from Schmitt Enertec, a German-based company specialising in gas-powered engines from 140 kW to 500 kW. These are supplied locally by Energas Technologies.
The Energin CHP gas engine is equipped with all the pumps and heat exchangers on a base frame.
A 12-cylinder Energin engine running at sea level can produce 500 kW electricity at an efficiency of 42.1% if running on natural gas or CNG; and 42.7% if fuelled by biogas. It can also deliver 450 kW running on LPG at an efficiency of 36% and 250 kW if using woodgas at an efficiency of 35%.
To increase fuel-to-energy efficiency, the heat of the engine jacket water can be recovered through an engine mounted heat exchanger to produce hot water, which can be used for domestic heating, for example. At the same time as this Energin engine produces 500 kW of electricity, it can produce 255 kW of free thermal power, giving an overall efficiency of 63.6%.
More heat can be recovered from the exhaust gas to push efficiency up to 87.5% by producing 539 kW thermal power in total, and, if required, steam can also be produced from the exhaust heat.
The Energin CHP (combined heat and power) engine is equipped with all the necessary pumps and heat exchangers on a single base frame. The engine can also be combined with absorption chillers to use the heat for air conditioning in a process called tri-generation. This is ideal for hospitals and shopping complexes.
The overall running costs of solutions such as these are very competitive with grid power and ideal where grid power is not available due to limited infrastructure. Noise is not a problem, either. With an optional sound enclosure mounted on the base frame, noise can be reduced to a level below 70 dB at 1.0 m.
Energin engines can be equipped with a control unit to run several engines in parallel mode, without a grid connection, or in synchronisation with the grid. They can be remotely monitored and require an oil service only after 2 000 hours (three months running 24 hours per day).
Energin units are available in South Africa from Jetpark-based Energas Technologies.
Energas Technologies contact:
Laetitia Jansen van Vuuren
Tel: +27 (0)11 397 6809
Email: laetitia@energas.co.za
