Renewable Energy

I am going to go through some of the common forms of renewable and sustainable energy. Each has its own advantages and disadvantages which need to be considered. The first thing I would like to point out however is that we have enough easily tapped renewable energy along a small part of our coastline to power Australia many times over. The energy is free, however transmitting it from large capturing regions to modern cities in a reliable, efficient and safe way is the challenge. Where a 5 stage coal fired power station can sit churning out power most of the time, renewable energy can be intermittent, which means that to supply the same overall power through the same system, we would need far greater capital expenditure on transmission infrastructure. Furthermore, there is little incentive in Australia to clean up our emissions, which means people, governments and companies will usually opt for the cheaper dirty option, even though the long term cleanup and rehabilitation of cleared and mined land is considerably more.

What are the different types of Sustainable Energy?

Wind

Wind energy is the fastest growing form of renewable energy in the world. Wind is free to capture, and along many coastal areas there is a massive untapped source of clean energy. There are some costs involved in producing the wind turbines themselves, however once capital investment has been made, they will slowly pay themselves off. As the number and variety of wind turbines increases, the cost of turbines will gradually come down as long as supply can keep up with demand.

The largest disadvantage that comes with using wind power is its intermittency as wind speeds can quickly change from a strong force to a lull in the matter of minutes making it difficult to put large wind farms on systems which do not have the equivalent capacity of backup gas generation on standby.

Solar

Solar Photovoltaic (PV) we are perhaps familiar with, and without a doubt, many people coming to this site are hoping to find out about solar schemes. The advantage with solar panels is that they produce energy at a time when often we use the most of our energy. By installing PV, we not only reduce total energy demand on the system, but we reduce the peak load of the system, which for the hotter climates in Australia is during our scorching hot summer days. Therefore the value in demand management is significant as it reduces the need to upgrade transmission and generation infrastructure. Of course a large contingent of the population needs to adopt solar PV in order to achieve this and we are currently sitting at a penetration of around 0.9% of the population. In fact there is a greater percentage of people in very cloudy and cold environments that have adopted solar PV to offset their energy use.

Solar Thermal energy unlike solar PV, generates energy directly from heat, and not through electricity producing solar cells. Often solar thermal systems use large farms of mirrors to focus light on a central thermal chamber which is used to drive a turbine (just like a coal fired power station). The technology for thermal power stations has been around for over a century, however finding cheap ways to make masses of reflective or curved mirrors cheaply that will stand the test of time has been the barrier to solar thermal entering the market. Curved troughs can also be used to heat pipes of water which force compressed steam to a centralised generating unit. Of course when the sunlight disappears, so too will the thermal heating process, however companies have found ways to store energy in either graphite rods or molten salts so that generation can continue during the night.

Geothermal

Perhaps one of the most promising sustainable energy sources as geothermal energy is base load energy meaning that it can provide clean energy 100% of the time. In order to set up a geothermal plant, two holes are drilled down to a depth of around 5km where the temperature of the rock is a few hundred degrees Celcius. Explosives are then used to shatter and fragment the rock so that water can pass between the two wells. Heated steam is then driven back up the second well into a thermal power station.

Although this form of energy production looks like the most promising substitute for coal and nuclear power stations, there are a few draw backs. Firstly the hot rocks will eventually cool down over 30 or so years and the power station must be relocated to new bores. The rock will then gradually heat up again meaning that the energy source although by strict definition is non renewable, it is sustainable (i.e. we can tap as much geothermal energy from the Earth's core without inflicting permanent damage on that energy source for future generations. Sulphur which can be used in fertilizer and hydrogen which can be used in fuel cells can be separated and captured from the return water or high pressure super heated steam. As the system is a closed loop, water loss is minimal.

Hydropower

Hydropower is the most common form of sustainable energy used today. Although the potential for further exploitation of hydro energy is possible, often this is done at the expense of pristine wilderness sanctuaries high in the mountains. When a wall is installed to dam a reasonable head of water, many thousands of hectares of land is lost to damming, and through the rise and fall of water levels, skeleton mud covered trees line the rim of the dam making it both an eyesore and environmentally destructive. However when you look at the equivalent damage a coal fired power station does to a larger area of land, a case can sometimes be made to set up a hydro scheme.

Most of the easily accessible areas in the world are however already utilised and most hydro systems these days are small scale systems designed to make use of free flowing rivers and small water catchment areas. Hydropower can also be used as a form of energy storage by pumping water up a hill and regenerating the stored potential energy at times of peak demand. In other words you are basically building a big battery using water. Again this requires steep hills close to generation stations which is not always available, especially in many parts of Australia. Although hydropower is indeed an important mix in the sustainable energy spectrum, we will not look into it too deeply on this site as the process, technology and potential sites have already been well understood and exploited.

Wave Power

Wave power is generated from movement of water currents below the surface of the ocean. This is achieved by placing bouyant balloons about 15 feet below the surface and suspending from a pivot point which acts as a pump. Compressed water is pumped back through thousands of oscillating submerged buoys to a central generating station where turbines are moved in much the same way as a hydro scheme. If power is not required, water can be forced through a desalination process (reverse osmosis) to produce clean drinking water. This energy form is exciting as it (like geothermal) operates as base load power (meaning it produces energy 100% of the time).

Although one might think that energy was dependant on the wind speed, research has shown that actually the currents below the water surface are quite independent of wind above the surface making them ideal counterparts to coastal wind farms.

Biomass and Biofuels

Biomass is another important sustainable energy source provided it is used carefully to avoid displacing food crops and native bushland. In remote areas where the cost of transporting electricity is high, small biomass plants are used to fund mallee crops which are planted to reduce salinity. By burning this biomass closer to the point of use, a lot of energy loss is prevented and farmers can get heavily subsidised Mallee crops improving their soils.

Biofuels are often substitutes for petrol although the amount of biofuel available is very limited. If we wanted to replace most of our current petrol consumption we would decimate our food supply to make way for biofuel crops, which is definitely an unsustainable way forward, especially when there are other options out there. Some claim algae can produce hydrogen which could be used in fuel cell vehicles, although setting up the distribution infrastructure required for hydrogen vehicles would be very expensive.

Another exciting new technology is the use of Econol made from strains of Mycelium as talked about in the video below. We will have to wait to see if Econol production takes off.