October 19, 2017

The challenge of distributed generation in rural grids

And how smart wind turbines should deal with it

Distributed generation is the embedding of power generation units in the distribution grid.

Power generation technologies such as solar and wind energy, do not require large installations to be cost-effective: photovoltaic panels and wind turbines are very scalable and installed capacities starting from a few kW can deliver electricity at competitive rates. More importantly, the impact these installations have on their immediate surroundings is very limited: no large transports of fuel with the concomitant traffic of heavy lorries or railroad tracks, no large fenced-off areas around the perimeter to keep unauthorized staff away, no pollution in the form of carbon-dioxide.

It is thus no surprise that renewables have been the technology of choice when embedding power generation units in the existing distribution network.

This also explains why this silent revolution is spreading so easily: the addition of additional capacity is authorized (or halted) by local authorities without the need for lengthy approval procedures and expensive environmental-impact studies. The community will decide how its own electricity need will be solved by installing its own power plant.

This entails a reshuffling of the power business card deck: generating electricity is no longer the monopoly of one or a few very large companies. Instead, virtually anyone can become a utility company, or at least its own. These renewable energy technologies, spread out in many smaller units, have shown to deliver electricity consistently and reliably just as larger units. In fact, because of their distributed nature they have the potential to achieve an even higher security of supply then their large centralized counterparts.

Renewable-energy-based distributed generation is here because of the reasons above and is here to stay because it makes economic sense:

  • Even though the capital cost per installed kW is higher than in the case of large centralized units, this higher cost can largely be offset by the lower cost of grid-connection. Distributed generation does not need any additional grid reinforcement nor dedicated overhead lines.
  • the operational cost will be lower than large centralised thermal units because of the absence of fuel cost
  • The kWh produced by a distributed power plant is competing with the cost of a kWh delivered by a large centralized plant (including its cost of generation, transport & distribution). By bringing the generation close to the consumption of electricity, expensive steps in the process can be avoided.

And this is exactly where the going gets tough: for distributed generation to live up to its true potential, no grid reinforcement should be required. Adding additional generation capacity to the distribution grid, close to consumers that need it, should require no additional distribution network capacity. Copper needs to be replaced with intelligence, even when distribution grids are heavily loaded and their operators stressed.

More embedded power generation close to the consumers will cause problems related to both voltage amplitude and frequency. Standard voltage-regulation methods assuming one-way electricity flows are no longer adequate when excess power is going “upstream”. The delicate balance between generation and consumption is much harder to maintain with a large fraction of scattered units that cannot be dispatched as large centralized plants.

Distributed renewable-power generation will thus have to cope with increasingly-saturated distribution grids and it will have to do so relying on the controllability of its power source and the flexibility of the loads it is serving. The case for distributed wind is even more challenging: good wind resources are found in remote areas where grid connections tend to be weak or grids are not interconnected because they serve island communities.  The challenge of distributed wind is exactly to enable increase of power consumption at the connection points without the need for grid reinforcement. It is then that distributed wind truly delivers and cashes in on its advantage over centralized power units whose energy will need thicker cables all along the way from the power plant to the final customer.

Wind turbines will need excellent controllability of their power output in spite of the variable nature of their prime mover. In addition, seamless integration into a higher-level energy management system will be a prerequisite for introducing wind power in such stressed grids.

Why XANT?

XANT turbines can provide the necessary on-site generation capacity increase, without the costly interconnection upgrade. The customer at the end of the rural distribution network is exactly who XANT had in mind from the very start of the design process.

XANT turbines adapt to a wide range of grid conditions and can accommodate various energy management strategies. XANT turbines are equipped with a two-way SCADA system that can receive both active and reactive power set-points. In addition, control algorithms can be activated to support the grid voltage and frequency without any need for communication.

On top of the standard features, the XANT technology enables high degrees of wind energy penetration without increased complexity due to 2 optional systems:

  • The integrated Energy Storage Unit (ESU) smoothens out the variable nature of wind power and allows for perfectly-controlled power output ramps which are well within the ramp-up & – down times of most diesel genset controllers.
  • The integrated Dump Load Controller (DLC) can autonomously turn on and off non-critical loads or loads with inherent storage (e.g. water pumping, space heating…) This simple but effective strategy of balancing generation and demand can enable the integration of more wind on the local grid without very limited additional costs.

At XANT we believe distributed generation will play an ever-increasing role in the power market. XANT wind turbine technology is ready to contribute to this paradigm shift in the most cost effective way.

XANT is pleased to advise that its entered into a sales partnership with Steam Generation in the African markets

Alex DE BROE, CEO

www.XANT.com

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