Hydroelectric turbines can be combined with solar panels, diesel generators and battery storage to generate off-the-grid renewable energy 99.99% of the time.
The Potential Need For Hydro-Power Development
Economic growth and the access to electricity are directly related. Therefore, countries with low electrification rates are looking for new ways to cover their energy demands with cleaner and more reliable sources of energy.
Popular green energy sources such as solar or wind have seen a steep increase in installed capacity over the latest 10 years. Actually, according to REN21, solar has increased from 15 GW installed in 2008 to 505 GW in 2018 while wind power has increased from 121 GW in 2008 to 591 GW in 2018. Even though these have been the energy sources with the highest growth in the last decade, they are also the ones who provide the highest instability to the electrical supply.
Due to the nature of unstable solar radiation and wind speeds across the year, these energy sources have an irregular generation curve pattern that needs grid or battery-support to provide a reliable electrical service to the power system.
Nevertheless, the disadvantage of installing an off-grid solar system is that the battery bank or energy storage system needs to be too large in order to cover-up all the electrical loads, which translates into very high capital costs. Moreover, batteries are extremely sensible to temperature variations and also to humid environments.
Regions with no access to an electrical supply from the power grid are more vulnerable in this aspect, limiting their availability factor throughout the year by reducing the autonomy of battery banks to make projects economically feasible and also limiting the amount of energy that each household can consume.
However, there is another source of power that has the most reliable and extensive potential to provide energy, not only for a single household but for a whole community, town or even region, we are referring to hydro-power.
What Is A Small-Scale Hydroelectric Power Plant And How Does It Work?
Basically, hydropower uses the energy from rivers to move specialized turbines that are able to harvest the flow speed and transform it into mechanical energy that can later be transformed into AC electricity by a generator.
Most famous hydroelectric power plants have capacities above 30 MW which are intended mainly for large scale projects that supply large amounts of electricity to the power grid of any country. However, developments in technology and the reduction of costs has allowed for this energy source to also be applied at a smaller scale.
That’s how micro-hydropower plants went into the market and started increasing their installed capacities worldwide. Micro-hydro power plants are small scale hydroelectric generators that can generally produce up to 200kW of electricity with a single turbine.
In other words, micro-hydro projects are now possible even on sites with a lower flow of water or a lower elevation drop, making them suitable for rural development in isolated regions while offering a decentralized energy source without the need for grid-connection.
Hydro-Power vs Other Renewable Energy Sources: The Technical Advantage and Issue of Hydropower
As it was mentioned before, solar and wind energy sources have unstable power curves that do not necessarily match the consumption patterns of the user, making them unsuitable without energy storage. Meanwhile, micro-hydro energy is very stable, providing an almost constant power output throughout day and night.
Wind turbine power curve, Blade Cleaning
Solar power curve, Bridge To India
SHP power curve, Turbulent
Capacity Factor and Efficiency
The capacity factor is a parameter that gives a reference for the actual electrical energy output over a given period of time to the maximum possible electrical output. In other words, provides a reference for the performance and actual usage of all the components installed. Also, efficiency is a value that provides a reference for the amount of energy available at the site and how much of that energy is actually transformed into electricity.
While a typical solar power plant has a capacity factor between 10-30%, a SHP plant can have a capacity factor as high as 90%. In the same aspect, while a premium solar panel commercially has around 20% efficiency, an SHP can have an efficiency that is as high as 90%. This means that SHP plants take much more power out of their energy source than solar panels can ever do.
Solar panels need a lot of open area in order to provide an amount of power that can be sufficient enough as to power typical household and community appliances. An equivalent micro-hydropower plant can require as little as 6% of the space needed from solar panels to power a community.
This is especially valuable for rural populations located in jungles where making space would require to cut down many trees.
Shading, Thermal and Soiling Losses
PV systems have three great enemies in their power performance. Even when the best solar resource is available and the highest efficiency module is installed, solar panels' performance gets drastically reduced if shadings caused by external objects such as trees or buildings block the sunlight. Moreover, some regions with good solar resources, also have very high ambient temperatures which, ironically, also reduce the performance of the solar panels drastically. Furthermore, arid or highly polluted regions can also generate high levels of dust that when impacting the solar panel can stick to the glass surface blocking the sunlight and reducing performance.
Meanwhile, micro-hydropower has no external factors influencing performance other than depending on the resource itself, the flow of water.
Hybrid Hydro-Solar Power Generators: The Need for Reliability
As mentioned above SHP is dependent on the flow of water, this means that even with a 90% capacity factor, there is a time in which the SHP reduces its power output. This is generally associated with the dry or summer season where the water bodies are evaporated and the flow of water reduces.
No single renewable energy source can ever cover entirely the whole energy demand throughout the year because they depend on environmental conditions that are not controllable.
However, there is an important factor to notice between hydropower and solar energy. They have opposite peak time performances. In other words, when hydropower is high (raining season), solar power is low (cloudy, no solar radiation), meanwhile when solar is high (summer) hydropower is low.
This contrast offers an interesting approach on how to offer a 99.99% uptime with a system that is able to cover the energy needs of the community throughout the year: a hybrid hydro-PV system! By using hydropower as a primary source, the highest amount of energy loads can be covered throughout the year while solar power is used to provide that extra energy required during the summer season or other peak energy demands during the day. Under this configuration, battery banks or diesel generators can be connected to the system to provide backup to essential and peak loads during these times in which the flow of water throughout the river or stream is low.
The combination of these decentralized energy sources allows rural communities throughout the world to have a 99.99% reliability in their energy supply, independent from the power utility companies, that allows them to live entirely off-the-grid.