Power Generation

General

Electricity is “normally” the energy provided to homes, business, farms and the raw materials industries and is primary generated by major grid-based organisations who have to transmit that energy many miles across the country to its customers and consumers.

What if that energy can be provided locally by natural means?

Natural methods of producing local energy fall to Wind, Water, the Earth itself and the Sun. It could, also, be in the form of both mechanical and electrical outputs.

The grid systems for electricity and water distribution would still be required as naturally derived power, in its raw state, is both variable and dependent upon local weather conditions.

However, locally derived natural power will enable the country's reliance upon imported fossil fuels to be reduced and also, to reduce (not remove) the necessary level of the inevitable development of nuclear power required in the future.

Wind Energy

Horizontally aligned wind-turbines (HAWT)

Horizontally aligned wind-turbines are those that are most commonly seen, and have been so for several centuries.

On these machines, where the blades central axis can be automatically turned into the wind by a balancing vane to allow it to operate at all times that there is sufficient wind to overcome the natural physical reaction to turning, the wind-catching blades are vertically set and the driving shaft from those blades is set in the horizontal plane.

Wind-turbines of this configuration have been historically used in the strictly mechanical sense for, say, lifting water from wells, for driving larger mechanical equipment such as grinding mills, lathes and the like.

There is absolutely no reason for these mechanical uses to be discontinued where they perform suitably, and with reasonable efficiency, taking into account all of the local circumstances.

Their power is transmitted by direct-acting universally-connected shafts from the windmill blade head to the device(s) where gearboxes and power take-offs may be utilised to connect to several machines including possibly a generator.

Coupled, either directly or indirectly, to generators, electricity production is possible and this can be seen in use in many parts of the world today, from the smallest system on, say a boat, or at a remote monitoring station and producing just a few mA, to the largest with 100 to 150m diameter blades than can supply many kW. and are normally located at sites that have a high wind ratio.

In housing and small commercial applications, such machines are more usually to be seen at remote, off-grid locations and powering such things as fridges, televisions and washing machines as well as lighting and communications systems.

HAWTs are very rarely seen in modern domestic community and urban situations because of their visually intrusive nature, relatively low efficiencies and the possibility of insufficient wind to turn the turbine, although this situation is gradually changing along with peoples perceptions of turbines.

The siting of such turbines is not an easy art. Many things can affect how much wind will be available to drive the machine. Even another machine sited nearby can “steal” the wind from yours if they are not suitably sited in relation to each other.

Although the minimum required windspeeds are falling due to improved blade design, bearing design, coil and stator materials technology advances and motor conversion efficiencies, it should be understood that, at this time, a minimum mean wind speed of approximately 8mph is usually required to turn the unit and start to generate.

At the other end, windspeeds above 40mph are usually considered to be dangerously high and the machine is feathered to attempt to ensure no damage occurs to it and to reduce any possible mechanical disintegration.

Vertically aligned wind-turbines (VAWT)

Technology is always developing and expanding the known barriers of all manner of ideas and capabilities.

Alongside the ever-continuing development of HAWT technology in terms of blade and control development, vertically aligned wind turbine (VAWT) technology has also developed.

In this situation, the blades rotate around a vertically aligned shaft and the power transmission is also directly coupled in that direction. These units usually exhibit a helical blade configuration to maximise their exposure to winds from any direction as they do not have to turn into the wind.

It has also been established, in trials at various locations around the globe, that VAWT is potentially capable of being utilised in areas of significantly more severe weather conditions and limiting extremes than HAWT. It can also successfully operate physically closer to the ground than HAWT and at much lower windspeeds for the same output efficiencies. Its upper-end windspeed operational limits are also potentially higher.

This vertical configuration should, with continuing further development, allow for smaller blades that can be located within a smaller operating envelopes and be independent of any prevailing wind direction.

Whilst still very much in their “teenage” years of development, and as is normal with all major research, the development is of the commercial rather than the domestic scale, it is hoped eventually, that this configuration will allow the whole device to be constructed as part of the building roof structure.

Theoretically, if required, it could be almost totally disguised within the structure, but the aero-dynamics and the energy capture of the turbine might be significantly compromised in so doing.

Development of this technology is ongoing and should eventually produce high efficiency turbines located in previously unattainable areas and configurations.

Water

As with wind power, man has harnessed water for centuries as a source of mechanical power to drive various machines such as pumps, mills and manufacturing processes.

Water, when passing horizontally, and with relatively high inherent kinetic energy, through say a mill-race, can turn a paddle wheel (over-shot, under-shot, centre-run, pelton, etc.,) which, through a gearing device, can turn many other forms of machine.

Similarly, relatively small amounts of water falling from above, this time with relatively high potential energy availability, through a pipe to provide direction, can have sufficient power propel a turbine wheel to, once again, drive machinery.

One system uses large, relatively level slow-moving, volumes (utilising high kinetic energy) and the other uses relatively low volumes, but at a higher velocity due to a fall from large height (high potential energy) to achieve the similar results. Either, or both, can be potentially utilised for any energy using situation.

Hydro-electric

It will come as no surprise therefore, to realise that, as with wind power, water-power can also be harnessed to produce electrical power.

Hydro-electricity is that electricity produced when a generator rotor is turned within a magnetic field and, with sufficient power, by the action of water passing over a paddle wheel connected to that rotor.

H-E can be produced either by a water-course running large water volumes at constant flow through a mill-race and turning a water-wheel that is connected directly, via a gearbox, or belting, to a generator rotor shaft and thereby utilising the kinetic energy encapsulated within the large moving water mass.

H-E can also be achieved by allowing water to fall in a controlled manner through pipes from a higher level to that of the generator and which are connected to an enclosure that surrounds the paddle-wheel. This directs the water to pass over, and drive, the paddle-wheel which will turn the generator to produce electricity. (This time the high potential energy of the smaller volume of water is converted to kinetic energy to drive the machine)

NOTE:- Water power at Morwellham Quay on the River Tamar in West Devon, worked an over-shot wheel in the 17 / 1800's for it's various mechanical and mining processes (still in situ). Also still in use on the site today after nearly 100 years, are pelton-wheel driven hydro-electric generators supplied with water from a canal located several tens of metres above and which still provides electricity to the National Grid and is currently owned and maintained by Western Power Developments.

The Sun

Solar-PV Arrays

All built structures will have elevations facing both energy-positive and energy-negative directions. Dependent upon where the structure is geographically located in the world, these elevational effects, with respect to the particular structure being considered, will vary in terms of their effective strike angle to the mean solar aspect of that structure.

In the UK, the negative face would generally be the north elevation and the sun's mean angle (solar aspect) would be approximately 35° above the southern horizon. This angle, however, varies daily throughout the year and minute-by-minute throughout each day, no matter where the structure is actually geographically located on the world's surface.

Building elevations in the UK that will exhibit the greatest requirement for energy input, and are the least effective in attracting absorbable free energy, are those north-facing aspects.

Solar-PV is short for Solar-derived Photo-voltaic cell and is the term for a device that converts, in this particular instance, solar-derived light into electricity. However, any light source is effective and even moonlight has been known to produce an output from high-efficiency solar-PV panels.

The panels will produce electricity with light simply falling upon them. However, the clearer and brighter that light is the better for performance, but it is not unknown to mount them even onto north-facing roofs and to even mount them vertically as a building façade (BIPV).

The reactive effect of light on certain materials and combinations of materials was first noted seriously by Edmund Becquerel over 170 years ago, back in 1839, when he noticed that where light was allowed to fall onto the terminals of some battery plates he was experimenting with, a small, but notable increase in battery voltage was evident.

This phenomenon is called “The Photo-voltaic Effect.”

In solar-PV cells, when LIGHT strikes the surface of a silicon based mono-crystaline, or semi-crystalline cell, it produces a small electrical current. By connecting many of these cells together, sufficient power can be developed to provide most structures with usable amounts of electricity.

Combining modern electronics with solar-PV units, all manner of remote monitoring and signalling devices are now capable of being utilised and installed in locations only previously dreamed of.

Marker buoys at sea can now be powered, alarmed and have their status transmitted to land-based monitoring stations and to ships in the area; remote pumping stations can be monitored and secure systems can be controlled, again with their status being continuously transmitted to central control stations; highway signs and lighting can be powered and controlled without the need for complex cabling networks, etc., etc.

It is now possible to install these cells into both the domestic and commercial environments, replacing the “normal” building finishes with pv panels and producing, in some instances, sufficient electricity to export the excess back to the grid provider when requirement circumstances allow.

(BIPV) - Building Integrated PV - can be fully integrated into, say, a vertical wall cladding, or into a tiled / slated roof, with the “normal” constructional skin materials being totally or partially replaced by the solar-PV panels and forming a complete weather-tight and flashed-in roof or wall section.

With today's materials technology, the external visual appearance of a structure can be such that the presence of PV panels is not even recognised.


 

Some roofing manufacturers have already developed “slates” and “tiles” from solar-PV material and which can be directly laid in place of their standard counterpart.

Materials have recently appeared on the market that will allow the replacement of “flat-roofing” flexible roll materials with PV integrated films materials that utilise similar “thin-film” deposition techniques to that used in the silicon-chip industry.

As with solar-thermal panels, to achieve maximum results, the solar-PV panels should where this is possible and if the architectural arrangement allows, be laid so that they are always situated with their maximum surface area pointing directly at the sun's mean axis for its particular geographic location.

However, the solar elevation above the horizon is dependent upon physical location of the arrangement, the time of the year and to the fact that the sun tracks across the sky during the course of the day.

In the northern hemisphere, and at the latitudes of, say, Devon and Cornwall, providing that the mean axis of the panel array is between South-east and South-west and the panel array is angled at approximately 35° from the horizontal, then maximum possible absorption from a fixed position system should be achievable for that particular geographic location.

It is possible, with today's array technology and with the right budget being available, to continuously track the sun's actual position in the sky, both longitudinally and in elevation, throughout the entire day and at any time of the year. This has the obvious potential to significantly increase the amount of solar energy capture especially if fixed mounting surfaces in the correct direction and elevation are restricted to any significant degree.

This additional feature obviously requires motive power to enable it to monitor and track the sun. It also contains moving parts which require maintenance, repair and eventual renewal if it is to maintain the additional energy acquisition that the additional capital expenditure should be able to theoretically achieve and it requires to mounted on a flat surface.

NOTE:

Do not forget that a lack of direct sunlight, clear blue skies, “correct” elevation and “correct” direction of solar collectors - be they thermal or pv, will NOT prevent solar equipments from being successful.
 
These factors WILL affect their collecting efficiency and therefore the amount that can be collected and utilised by them.
 
They will work on NORTH-FACING ROOFS and walls, in the vertical and horizontal plane and even in clear moonlight!!!!

With acknowledgement for use of images to: