The smallest of the Canary Islands, El Hierro, has a way of combining hydro and wind power that may allow it, one day, to get all its energy from renewable sources. In August it went for two hours without using its diesel power station at all - but this could be the start of a bigger green transformation.
For more than 30 years, El Hierro has been dreaming of becoming self-sufficient. And this year it took a big step forward. At the end of June its new hydro-wind facility, Gorona del Viento, came fully on stream and in July and August it provided roughly half of the island's energy needs.
That means the island's 10,000 inhabitants are suddenly less reliant on supplies of diesel arriving over unpredictable seas from Tenerife, 200km away.
The system consists of five wind turbines with a total capacity of 11.5MW and two water reservoirs - one at 700m above sea level, the other down near the coast. The reservoirs are connected by two 3km-long pipes, and any water running from the upper to the lower reservoir passes through a series of water turbines, generating electricity.
Fresh water is used, rather than sea water, to ensure that the aquifers are not contaminated if there are any leaks.
What's unique about it is the way the wind part and the hydro part work together.
"When we get enough wind from the wind farm, we produce electricity and distribute it through the grid. Whatever is left, we use it to pump water from the lower reservoir to the higher one, and then, when the wind drops, we let that water fall through a set of hydraulic turbines and we generate electricity again for the population," says Juan Gil, chief engineer at Gorona del Viento.
The key disadvantage of wind power - the unreliability of the supply - is made up for by the water in the upper reservoir which can be released "within milliseconds" according to one of the engineers involved, whenever the wind starts to blow less strongly. The system is continually switching between releasing water from the upper reservoir and pumping water back up, depending on the strength of the wind and the demand for electricity.
But the goal is to go total wind power The length of time Gorona del Viento can continue generating hydro power is determined by the volume of the smallest reservoir - in this case, the lower one, which is less than half the size of the upper one. As soon as the lower reservoir is full, hydro generation has to stop because fresh water, which is in short supply on El Hierro, cannot just be released into the sea.
"El Hierro suffered many droughts and people were forced to emigrate to the bigger neighbouring islands, and to Cuba, Argentina and Venezuela," says Padron.
There are no rivers or lakes on El Hierro, so the only way to get water was from underground aquifers reached by deep shafts. Nowadays, there are also three desalination plants - running these, and pumping fresh water to villages at higher altitudes, consumes half of the island's electricity.
Another plan to offer incentives to persuade residents to swap their 6,000 conventional petrol and diesel cars for electric ones over the next 10 years.
Another is to build a composting plant that would turn half the island's rubbish into agricultural fertiliser.
There are also proposals to improve the efficiency of the water distribution system, and to experiment with wave power - Allende wants the island to be a place where green technology is put to the test.
Large numbers of foreign scientists and policy makers have already been visiting El Hierro to learn about Gorona del Viento.
Long term plan is to make all the islands green
For more than 30 years, El Hierro has been dreaming of becoming self-sufficient. And this year it took a big step forward. At the end of June its new hydro-wind facility, Gorona del Viento, came fully on stream and in July and August it provided roughly half of the island's energy needs.
That means the island's 10,000 inhabitants are suddenly less reliant on supplies of diesel arriving over unpredictable seas from Tenerife, 200km away.
The system consists of five wind turbines with a total capacity of 11.5MW and two water reservoirs - one at 700m above sea level, the other down near the coast. The reservoirs are connected by two 3km-long pipes, and any water running from the upper to the lower reservoir passes through a series of water turbines, generating electricity.
Fresh water is used, rather than sea water, to ensure that the aquifers are not contaminated if there are any leaks.
What's unique about it is the way the wind part and the hydro part work together.
"When we get enough wind from the wind farm, we produce electricity and distribute it through the grid. Whatever is left, we use it to pump water from the lower reservoir to the higher one, and then, when the wind drops, we let that water fall through a set of hydraulic turbines and we generate electricity again for the population," says Juan Gil, chief engineer at Gorona del Viento.
The key disadvantage of wind power - the unreliability of the supply - is made up for by the water in the upper reservoir which can be released "within milliseconds" according to one of the engineers involved, whenever the wind starts to blow less strongly. The system is continually switching between releasing water from the upper reservoir and pumping water back up, depending on the strength of the wind and the demand for electricity.
But the goal is to go total wind power The length of time Gorona del Viento can continue generating hydro power is determined by the volume of the smallest reservoir - in this case, the lower one, which is less than half the size of the upper one. As soon as the lower reservoir is full, hydro generation has to stop because fresh water, which is in short supply on El Hierro, cannot just be released into the sea.
"El Hierro suffered many droughts and people were forced to emigrate to the bigger neighbouring islands, and to Cuba, Argentina and Venezuela," says Padron.
There are no rivers or lakes on El Hierro, so the only way to get water was from underground aquifers reached by deep shafts. Nowadays, there are also three desalination plants - running these, and pumping fresh water to villages at higher altitudes, consumes half of the island's electricity.
Another plan to offer incentives to persuade residents to swap their 6,000 conventional petrol and diesel cars for electric ones over the next 10 years.
Another is to build a composting plant that would turn half the island's rubbish into agricultural fertiliser.
There are also proposals to improve the efficiency of the water distribution system, and to experiment with wave power - Allende wants the island to be a place where green technology is put to the test.
Large numbers of foreign scientists and policy makers have already been visiting El Hierro to learn about Gorona del Viento.
Long term plan is to make all the islands green
