Lincs offshore wind farm gained government consent

On October 21, 2008 Centrica received the official consent to develop a 250 MW offshore wind farm, off the Lincolnshire coast (UK).
Lincs project will be situated at 8 km off the coast east of Skegness and will be next to the recent offshore wind farm developments at Lynn and Inner Dowsing, currently the biggest offshore wind farm in the world.
The completion of Lynn and Inner Dowsing offshore wind farms (194 MW rated power in total) has taken UK in to the lead of world offshore wind industry, bringing UK total installed capacity to a total of about 600 MW. The installation of all the wind turbines was completed during last summer and at the moment 45 of the 54 3.6 Siemens turbines are fully commissioned and producing power. The wind farm is expected to be fully operational by the end the year.
Centrica has also in the pipeline two further projects off the Lincolnshire coast: “Docking Shoal and Race Bank”. These two further offshore wind farms will give further support to Centrica to become a big player in the renewable energy sector, adding 1,000 MW to their wind generating capacity.


Posted by: Filippo

Solar Planes are becoming a reality

Solar aviation traces its roots to the early 1970s, when hobbyists and engineers began using solar cells to power model aircraft. Then, since late ’90 endurance solar flights (day-night cycle) have been realized mainly on unmanned planes. Last summer an unmanned solar plane named “Zephyr” was capable to stay in the air for more than 82 hours (about 3 and half days!). The plane was running on solar power during the day and batteries that were charged by the sun, at night.
Other companies and organizations have also developed similar planes. A solar craft called “SoLong” flew for 48 hours in 2005. The US space agency “Nasa” developed “Helios” vehicle that set and altitude record in 2001 for a non-rocket-powered winged aircraft when it flew up to 29.5 km of altitude.
However, not only unmanned flights have been realised. The Swiss balloonist Bertrand Piccard plans in 2010 to launch “Solar Impulse”, a manned plane in which, in five year time, he will attempt to circumnavigate the globe. A transatlantic flight is planned to be realized already in 2011. In order to be capable to carry a pilot the craft will have a huge wingspan of about 60 m. Furthermore because the plane will be piloted by only one person at time, it will have to make frequent stops and break the journey into various legs.
In May 2008 two Solar Impulse pilots (Bertrand Piccard and André Borschberg), one after the other, spent 25 hours flying non-stop at the controls of a virtual flight in a cockpit identical to the one of the Solar Impulse. The pilots were able to test the ergonomics, the aerodynamic behavior of the plane, the management of the energy consumed by the motors or stored in batteries and the efficiency of these during nocturnal part of the flight.
Being photovoltaic cells capable to produce little amount of power (about 125 watts per square meter with good/optimal solar radiation) the only way to make an airplane flying long distances with so little power is to make it light and with a big wingspan. Solar panels cover almost the entire top surface of the wings and tail.
The prototype should be available by the next summer and the earliest flights will be made under battery power without solar cells, but later tests will be done by applying the complete technology. The team hopes to make several 36 hours flights already in 2009 to demonstrate the ability to fly a complete day-night-day cycle powered only by the sun.
This kind of technology will not replace jetliners in the near future, but it is a great idea to show people what is possible to achieve with renewable energy.


Posted by: Filippo

Resources:
www.solarimpulse.com
www.nasa.gov/centers/dryden/news/ResearchUpdate/Helios/index.html

Heat Pumps: Renewable Energy or not?

Heat pumps are a means of converting work energy into heat energy in a process analogous to a reverse heat engine. Thermodynamically, an ideal heat pump cycle is the most efficient means of generating heat energy at a temperature above ambient - i.e. heating a room.

What is more, heat pumps extract most of this heat energy from the environment - a renewable energy source. A smaller part of the energy is supplied in the form of work energy, renewable or otherwise ....The heat transferred between a cool environment and a heated room for a given amount of work is theoretically given by the system's COP. For an ideal cycle operating between a environment at Tc and a heated room at Th this is given by 1/(1-Tc/Th). For typical exterior and interior temperatures of 10 degrees C (283K) and 20 degrees C (293K) the COP is an impressive value of more than 29.

This means that an ideal heat pump consuming 1kW of electric power for work delivers 29 times more energy than an electric element heater, with at least 28 kW of this heat energy being extracted, renewably, from the environment.

In real systems, with their non-ideal cycles and realistic system limitations, the COP rarely exceeds 4. Nevertheless, this still looks distinctly impressive compared to simple resistive electric and fossil fuel combustion heating systems. Who wouldn't want a heating system with an "efficiency" of 400% ? (more on the topic of heating efficiencies later maybe).

A so called "Primary Energy" analysis reveals a slightly different picture, perhaps. If the electricity is generated in conventional fossil-fuel combustion power plants, where work is generated from heat and then converted into electricity, a plant "energy efficiency" of 30% is quite typical. In the UK, for instance, the remaining 70% of the energy is mostly discarded as waste heat energy to the environment (in those distinctive wide parabolic-sided chimneys). If electric energy is used to drive a heat pump with a COP of 3.3, we have just recovered the heat energy initially lost to the environment - and we haven't even accounted for distribution losses. Now our "energy efficiency" appears to be well under 100%. Not as impressive! (conventional gas condensing boilers routinely exceed energy efficiencies of 90%)

So why not use the fossil fuel, on-site, in an engine to supply work directly to the heat pump and then capture the "waste" heat energy of the engine in our heating system - a classical co-generation approach. A quick calculation shows that a gas engine with a work efficiency of 25% driving a heat pump with a COP of 3.3 yields a primary "energy efficiency" of 158%. Now that's a bit better! ..... (unless these efficiencies of >100% are beginning to irritate you - in which case you'll have to wait for the next instalment on this topic)

Tidal power – Tidal stream generation

A relatively new technology, tidal stream generators draw energy from currents in much the same way as wind turbines. The best way to understand the mechanism of the generator is to think of it is an underwater windmill. The higher density of water, 832 times the density of air, means that a single generator can provide significant power at low tidal current velocities (compared with wind speed).

The advantage of this kind of source is its predictability (predictable as the phases of the moon).

Tidal stream power systems need to be located in areas with fast currents where natural flows are concentrated between obstructions, for example at the entrances to bays and rivers, around rocky points, headlands, or between islands or other land masses.[1]

First tidal power turbine got plugged to the network[2]

An underwater turbine that generates electricity from tidal streams was plugged into the UK's national grid on the 17th of July 2008. It marked the start of a new source of renewable energy for the UK.

Tidal streams are seen by many as a plentiful and predictable supply of clean energy. The most conservative estimates suggest there are at least five gigawatts of power in tidal flows around UK, but there could be as much as 15GW.
The trial at Strangford Lough, in Northern Ireland, uses a device called SeaGen (www.seageneration.co.uk). During the testing phase its power is limited up to 300kW. However, when it will eventually run at full power the turbine is expected to generate 1.2 MW.

SeaGen was designed and built by the Bristol-based tidal energy company Marine Current Turbines (MCT).

The cost of installing the marine turbines is £3m for every megawatt they eventually generate, which compares to £2.3m per megawatt for offshore wind. The costs will drop if the technology is more widely adopted.
After SeaGen will start to operate at full capacity the plans of MCT is to build a farm of turbines before 2011. Their next site will be off the coast of Anglesey and the initial farm will be about 10.5MW. It seams that the resource up there is around 350MW."

The Pentland Firth, the Channel Islands and the Severn estuary are also other potential hotspots for tidal energy in UK.

***************************************************
Tidal Power in the waters of the East River off Roosevelt Island[3]

At the other side of the Atlantic Ocean, near by New York, other people are also working to similar installations.

A third generation of experimental turbines has been installed by Verdant Power (www.verdantpower.com) in the waters of the East River off Roosevelt Island. The East River is not a real river, but a tidal strait connecting Long Island Sound to Upper New York Bay.

The first two generations of turbines were installed in late 2006 and early 2007 and the company gained a lot of knowledge from their breakdown and trouble shooting.
These kinds of generators have been designed so that they are automatically swung by the tidal currents and always face the right direction of the current. They sit on piles drilled into the riverbed and at low tide are six feet below the surface. Underwater power cable links the generator to Roosevelt Island.

The original turbine blades were fiberglass stretched over a steel skeleton, but apparently they broke on the first deployment. Thus, new blades were fabricated from aluminum magnesium, and they held up well, but the flowing water found the next weak point in the machines, along the rotors, or hubs. These snapped within two months. Now, the new generation is provided with new aluminum alloy blades fixed to hub.

In my personal opinion this kind of energy, if applied in the right places, could be another good example of renewable energy and could make a massive contribution to Britain, and to other countries with similar resources, cutting CO2 and fuel consumption. The main issue is that there are few places in the world where this kind of technology can be properly applied. My hoping is that tidal stream generation, like wind, will become a significant reality and contributor to the future mix of energy.


Posted by Filippo

Resources:
[1]: Wikipedia – accessed on September 3, 08
[2]: Guardian magazine, UK - Thursday July 17 2008
[3]: New York Times, USA - Thursday August 23, 2008

National Climate March 2008 – Saturday December 6th

Join people all around the world to demand action now to prevent future climate changes.

The “Call to Action” for these demonstrations and related events is:

“We demand that world leaders take the urgent and resolute action that is needed to prevent the catastrophic destabilisation of global climate, so that the entire world can move as rapidly as possible to a stronger emissions reductions treaty which is both equitable and effective in minimising dangerous climate change.

We demand that the long-industrialised countries that have emitted most greenhouse gases currently in the atmosphere take responsibility for climate change mitigation by immediately reducing their own emissions as well as investing in a clean energy revolution in the developing world. Developed countries must take their fair share of the responsibility to pay for the adaptive measures that have to be taken, especially by low-emitting countries with limited economic resources.
Climate change will hit the poorest first and hardest. All who have the economic means to act, must therefore urgently and decisively do so.”

More details or information about what’s going on in your country can be found at:

www.globalclimatecampaign.org

Take action - join the demonstartion


Posted by Filippo

Wave Energy – Pelamis

A Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The Palamis, one of these types of converters, was developed by the Scottish company Pelamis Wave Power - PWP (www.pelamiswave.com), it was the first world’s commercial scale machine to generate electricity into the grid from offshore wave energy.
The first full scale prototype was successfully installed and tested in 2004 at the European Marine Energy Centre in Orkney (Scotland).
The Pelamis consists of a series of semi-submerged cylindrical sections linked by hinged joints. The wave induced relative motion of these sections is resisted by hydraulic rams which pump high pressure oil through hydraulic motors via smoothing hydraulic accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from the system is fed down trough a submarine electrical cable to a junction on the sea bed and then to the shore network. Several devices can be connected together and linked to shore through a single seabed cable[1].
The world's first commercial wave farm is under development in Portugal waters, at the Aguçadora Wave Park near Povoa de Varzim. The wave farm will consist in three Pelamis P-750 machines resulting in a total rated capacity of 2.25 megawatts.

Aguçadoura wave farm:
Owners/Developers: Enersis / Babcock & Brown
Location: 5km off the Atlantic coastline of northern Portugal (substation at Aguçadoura)
Wave generator type: Pelamis P-750 (rated power 750 kW)
Total capacity: 2.25 MW (3x750 kW)

The Aguçadoura wave farm constitute both the world’s first, multi-unit, wave farm and also the first commercial order for wave energy converters. Additionally Enersis have issued a letter of intent to “PWP” for a further 20 MW of Pelamis equipment to expand the initial Aguçadoura project to a larger scheme. Development work for the second phase project is already under way. The Aguçadoura wave energy project in Portugal is supported by a specific feed-in tariff currently equivalent to approximately 0.23 €/kWh [2].

One of the three 750kW Pelamis machines due to be installed under the first phase of the Aguçadoura wave farm off Portugal has produced “several MWhs” of electricity during a short-term test run. All three machines should be deployed by the end of this summer before rougher seas arrive at the end of the season [3].

Future projects:
On February 2007 funding for Scotland's first wave farm was announced by the Scottish Executive. It will be the world's largest, with a capacity of 3 MW generated by four Pelamis machines and a cost of over £4 million. The funding is part of a new £13 million funding package for marine power in Scotland.
Pelamis Wave Power has also expressed an interest in installing Pelamis devices at the Wave hub development off the north coast of Cornwall, in England [1].

References:
[1]: Wikipedia website – accessed on 21/08/08
[2]: Pelamis Wave Power website – accessed on 21/08/08
[3]: Renewable Energy News – Issue 149 – dated 7 August 2008


Posted by Filippo

Overview of Floating Offshore Wind Turbine Concepts

During my specialisation curse, held at the National Technical University of Athens, I had to carry out an investigation on a free subject. Due to my previous background (naval architecture) I decided to look at floating offshore wind turbines.

The main topics of the report are described here below.

The concept of developing offshore floating wind turbines began in the early 70’s and Professor William Heronemus, from the University of Massachusetts, was one of the pioneers in investigating this kind of technology. The main research communities only appeared on the scene in the mid 90’s after the commercial boom of the wind energy industry.
The offshore wind industry will surely have a promising future in the North Sea and Baltic Sea off the coasts of Denmark, Netherland, Germany, Sweden, Belgium, UK and Ireland. However these kinds of installations are restricted to shallow waters. Except in some rare cases, most of the constructed or planned projects have a water depth up to approximately 20 m. In the case of water depth between 20 and approximately 50 m various fixed-bottom tripod and quadpod solutions have been proposed (e.g. Betrice Wind Farm in north eastern UK – jacket with sleeves for piles).
Highly populated coastal areas like northern Spain, western France, western Norway, countries facing the Mediterranean Sea, Japan, west and east coasts of USA and the east coast of China, where, due to high electricity demand and good wind resources, implementation of offshore wind farms would be ideal. However due to the fact their coastlines have high water depths (higher then 30-40 m) even after a few kilometres from the shore, the actual available technologies (fixed-bottom offshore wind farms) would be too expensive and not feasible.
In reality, floating structures, as shown in Fig. 1, have already been successfully developed by the offshore oil & gas industry over many years. As the concept has been successful in this industry it is credible to believe that also for the offshore wind industry a similar development (deep water installations) will be soon seen in the future.
Fig. 1 – Existing offshore oil & gas structures

The main challenges for floating offshore wind turbines are to combine stability and acceptable motions at low costs.
The main benefits for deepwater offshore floating wind farms will be the following:
- Greater choice of sites & countries
- Greater choice of concepts
- Greater flexibility of construction & installation procedures
- Easier installation, decommissioning and removal

1. Floating stabiliser classification
The floating structure has to provide enough buoyancy to support the weight of the turbine and to limit the motions within acceptable limits.
Limitation of the various motions can be obtained with different principles. Floating platforms can be divided into three main categories (see Fig. 2) based on their strategy used to achieve static stability:
1) Ballast stabiliser - SPAR: stability achieved by using ballast weights positioned in the lower part of a buoyancy tank, which creates a righting moment and inertial resistance to pitch and roll motions.
2) Mooring lines stabiliser – Tension Leg Platform (TLP): stability achieved through the use of mooring line tension.
3) Buoyancy stabiliser - FLOAT: stability achieved through the use of distributed buoyancy, taking advantage of weighted water plane area for righting moment.
Fig. 2 – Typical floating platform systems

2. Design challenges
The main dynamic challenges of a floating wind turbine are related to the combined wave and wind loads and the choice of blade-pitch control strategy. Typically, the overall architecture of a floating platform will be determined by its static stability driving the design parameter for the stabiliser due to the large wind overturning moment. However, as well as the rotor thrust force, the motions due to waves and current interaction are also important parameters to be taken into consideration at design stage.
The two main important design parameters are the flexibility of the wind turbine to operate within certain limits (max motions’ amplitudes and accelerations) and the breaking strength of the mooring lines. Winds, waves and currents are stochastic problems and due to their nature the prediction of the whole system’s motions is difficult to analyse with mathematical models.

3. Economic aspects
In order to keep the cost of the wind turbine itself within acceptable value, the movements and the accelerations of the whole system shall be kept within proper limits to be addressed by the manufacturers.
The economics of floating offshore wind turbines will be mainly dictated by the additional cost of the floating stabiliser, mooring system and power distribution system, which could be offset by higher and steadier wind speeds, proximity to highly populated areas and greater public acceptance due to lower visual and noise impacts.
Although the characteristics of proven offshore floating platforms used by the oil & gas industry are similar to the concepts being considered for floating wind turbines platforms, it is their differences that will allow the necessary cost reductions according to the following points:
- Oil platforms must provide additional safety margin to provide permanent residences for personnel. Wind platforms do not.
- Oil platforms must provide additional safety margin and stability for oil spill prevention. This is not a concern with wind platforms.
- Wind platforms will be deployed in water depths up to around 200 m. Floating oil tension leg platforms range in depths from 450 m up to 1,000 m.
- Submerging wind platforms minimizes the structure exposed to wave loading. Oil platforms maximize them above water deck/payload area.
- Wind platforms will be mass-produced and will benefit from a steep learning curve.

4. Environmental considerations
Implementation of offshore wind farms is less influenced by noise and visual impact constraints than offshore farms however other important factors have to be taken into account. Commercial shipping lines, fishing and fish breeding, birds migratory lines, military restrictions, oil & gas industry, dredging and conservation areas are some of the most important ones. As floating wind turbines are not restricted by their physical position (no limits on sea depth), it would be easier to find a suitable site for a wind farm (greater choice of sites) satisfying all the constraints.
Impact on the seabed would be less intrusive then fixed bottom structures. Furthermore the noise produced during installation process would be highly reduced.
At the end of the life of a project, turbines can be easily removed without leaving any permanent trace in the environment.

5. Current and future projects
For better understanding of what is going on around the world a brief description of undergoing projects is described here below.
5.1 Norsk Hydro – Norway
Norsk Hydro – Norwegian waters off Karmøy.
This demonstration project “Hywind” uses a Spar-buoy concept. Hywind (shown in Fig. 3) is designed such that all modes of motions that are exited by the wave forces have natural periods outside the wave frequency range. At the same time the pitch restoring force is such that the static tilt is sufficiently small.
This kind of solution would be acceptable only for water depth above 150 m, where a slender deep draft hull makes static requirements easy to fulfil and keeps moderate the wave loads.
Fig. 3 – Hywind concept

5.2 SWAY – Norway
The SWAY concept (shown in Fig. 4), similar to the Hywind proposal, is based on a floating elongated pole extending far below the water surface with ballast at the bottom part [10].
This system consists of a floating foundation capable of supporting a 5 MW wind turbine in water depths from 80m to more than 300m. The motions at the top of the tower are sufficiently small to allow the wind turbine to function efficiently.
Fig. 4 – Sway concept

5.3 BlueH - Holland
Blue H Technologies launched last December the first ever large scale prototype Submerged Deepwater Platform (SDP) which has been anchored in 108 meters waters at a distance of approximately 11 nautical miles from the coast in southern Italy (see Fig. 5).
This prototype is now used, not only to test the assembly, launch, float-over and installation of the tension legged wind energy converter, but also to serve as a metering platform.
The construction of the first real scale unit is now underway and will be soon moored nearby the prototype, to be followed shortly thereafter by other more units reaching the final rated capacity of 92 MW.
Fig. 5 – BlueH concept

On the 10th of March 2008 BlueH submitted a nomination for lease to the US Minerals Management service to install a 420 MW commercial wind energy project located at approximately 25 nautical miles from shore off New Bedford (Massachusetts) in a water depth of about 55 meters.

5.4 WindSea - Norway
WindSea is working to a new idea. A triangular floating platform having three wind turbines (see Fig. 6). One at each corner of the platform. Each platform will have a total rated output of 10 MW.
Statkraft, NLI and FORCE are the three companies collaborating together for this project.
Fig. 6 – WindSea concept

5.5 First floating desalination platform powered by wind
The Aegean Sea has the first floating desalination platform in the world. Fig. 10 shows the system that consists in a floating wind turbine plus photovoltaic panels. It produces the necessary energy used to turn seawater into drinking water and it is built in such way that can operate in the most adverse weather conditions, while the platform can be moved to different islands to supply them with drinking water.
Fig. 7 – Desalination platform

6. Conclusion
Deepwater offshore wind development could become practical with a proactive R&D agenda involving close collaborations between the oil & gas industry and the offshore wind community. Technical viability and cost effectiveness of this new technology for large scale offshore applications will be critical to securing financing and insurance in the earlier stages.
Cost is still the key issue for offshore wind, but beyond 30-40 m of depth it is credible to predict that cost increases will diminish with development of new concepts and lessons learned.
However interest in deep-water offshore wind is growing and future implementation of it will be surely seen soon in countries like USA, Japan, Norway and China. The main driver for this new industry will be the greater choice of sites and countries, greater choice of concepts, greater flexibility of construction & installation procedures, easier installation, removal and decommissioning.


Posted by Filippo