While many wind turbine components still include such an age-old element as iron, there is nothing of the kind to be found in rotor blades – they are all about chemistry.  This opens up opportunities if repairs are required because engineers can rely on repair kits with a good track record. 

Rotor blades are designed to last about 20 to 25 years. During this period, downtimes which are less hard on the blades alternate with periods of very heavy usage.  And then there is the huge impact of lightning or heavy hail. Wear and tear during operation and the normal aging process take their toll when it comes to how long the rotor blades last.

Stefan Brassel is Manager of Rotor Service and Sales at Deutsche Windtechnik GmbH. In his experience human error is another reason why damage is caused: “­Transport and assembly also cause damage.  And repairs that haven’t been done properly”. And the latter has the knock-on ­effect of one repair after the other. Brassel believes that damage caused by human error is up to 80 % – or in other words more than three quarters.

Human errors lead to damage

Even without looking at relevant surveys or statistics, the strong human factor that results in damage is obvious. “Other causes of damage are manufacturing defects that only become apparent during turbine operation,” points out service expert Brassel. Design flaws are among the top three causes of damage. Brassel goes on to say that “a lightning protection system that is badly designed results in frequent and severe lightning damage. Using too much adhesive at the trailing edge of the shell bonding leads to stress or shrinkage fractures that prompt a large number of cross cracks at the trailing edge”.

All these detrimental influences require a proactive ­maintenance strategy – which doesn’t cover all ­incidences of damage by a long chalk. Therefore, a number of repair companies with a good track record have sprung up that can repair damage of up to several square meters without having to dismantle the blades. And they are very quick too. Customers expect repair teams to have the ­necessary expertise and to keep turbine downtime as short as ­possible. Because every repair doubles the costs as ­operations are interrupted.

How do repair teams reach the sites? The choice is ­between rope access or elevated working platforms. Marko Wicha, Project Manager at Windigo GmbH, believes there’s no clear-cut case for either. The Berlin-based company relies on both. He explains: “There are pros and cons to both technologies. We recommend rope access for small repairs and elevated working platforms for large ones”. He goes on to say that rope access is not practical for large-scale or even structural repairs of laminate. He is not worried by the usual objection raised against using elevated platforms due to the wind. “When it comes down to it, engineers using rope access will be more exposed to the wind, for example when repairing blade tips”. And he points out that wind speed of 15m/sec would bring both methods to a halt.

Prevention is better than cure

Even before the rotor blade’s material is affected, internal and external impact damages the blade’s coating. Solid matter in the air, like sand or coarse particles of dust, are hard on the inflow edges in particular.  However, there is one thing Brassel is surprised about: “Contrary to all ­expectations, erosion at desert sites is not as bad as you might think considering the amount of sand there”. Brassel believes that the minor damage done to the ­inflow edges is due to the dust particles’ low weight.

However, the coating’s worst enemy is rain. Because of their relatively large weight and the high kinetic ­energy, raindrops have a damaging impact on the coating. In the end, erosion takes place in the fibre-reinforced ­composites. Erosion is especially strong when the ­kinetic energy generated from the drop height coincides with the rotating blades’ maximum energy – or in other words at the blade tips. The erosion is detrimental to aerodynamic properties and significantly diminishes energy yields.

While damage can be rectified through a general overhaul of the rotor blade, dismantling, repairing and ­assembling blades costs a lot of time and therefore money. The ­alternative is a polyurethane-based (PUR) coating on the suspended blade. This is usually sprayed on. PUR coatings are considered especially durable and have high UV ­resistance. The elasticity of the coating is one of the rotor blades key features. It absorbs the blade’s deformation well during a cycle without leading to crack formations. The usual thickness of a layer amounts to no more than just 300 micrometres.

Standardisation around the corner

Although the PUR coating needs to be renewed at regular intervals, it lasts two or three times longer than ­conventional coatings, according to Christian Claus who heads the Renewable Energy Business Division at 3M. In a coating magazine Claus says : “Prevention is more cost effective than repair at a later date” and gives an ­example. He states that the costs for a coating amount to ­approximately € 1,000 and goes on to say that by ­regularly ­carrying out maintenance and applying a PU-coating alone the increase in revenue could be € 100,000.

But it is not just damage caused that means the blade ­coating has to be superb.  Because the top coating ­dazzled it wasn’t popular in the past. Matt coatings ­provided the answer.

The blade coating has to suit such a variety of different requirements and applications that standardisation is a must. A standards committee has been working on a new version and summary of the relevant standard for several years. Some of the multi-section Coating Materials DIN EU ISO 4628 has already been published, but the ­majority can still be consulted by the public. Final publication – and therefore the point when it will come into effect – is expected this autumn.

Pioneering concepts create new opportunities

In order to minimize the risk of damage, defining a ­quality standard and enhancing the quality of ­manufacturing, ­assembly and transport is vital. Particularly since Brassel believes the job will not get any easier “because the blades are getting more complicated”. But he is also aware of the manufacturers‘ efforts to make the blades less repair-prone.  “An interesting aspect is that Siemens is making rotor blades without any bonded areas,” he says. “These blades are heavy, but work fine”.

Siemens is breaking new ground. The essential elements of a conventional rotor blade are two half shells made of glass-fibre reinforced plastics (GFRP). To achieve the finished result, engineers place the glass-fabrics together with the pre-fabricated reinforcing belts in a half-shell mould and evacuate the textile composite. Because of the low pressure, the resin is infused into the fabrics within two to three hours. The half-shell is then hardened at approximately 70 C° for several hours. Only the main belt inside the blade is made of CFRP. 

The high-tech material still has one major disadvantage,  CFRP is costly. Moreover, soaking the fibres during the infusion process is difficult. Currently, the ­manufacturers only make some of the rotor blade from CFRP. So the ­repair teams can carry on as they were for some time yet.

Jörn Iken

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Designed by Studiomobile architects Antonio Girardi and Cristiana Favretto, the Jellyfish Barge is an octagonal greenhouse set atop a 750-square-foot wooden base that floats atop 96 recycled plastic drums. The simple and low-cost design was created with adaptability in mind so that it can be applied to a variety of environments for long-term use. The compact and modular greenhouse can produce enough food to support two families, and can also be easily expanded with additional modules to support a larger community.

Related: GrowUp’s Aquaponic Urban Farm Produces Sustainable Fish and Vegetables in a Recycled Shipping Container

The crops are grown hydroponically and the fresh water is provided by seven solar stills designed by environmental scientist Paolo Franceschetti. The solar stills use fans and pumps powered by solar energy to suck in and purify water; the seven stills can produce up to 150 liters a day of clean, fresh water from saltwater or even polluted waters. The Jellyfish Barge uses a mixture of distilled water and 15% seawater to water the crops. The hydroponic system can be remotely automated and controlled.

+ Studiomobile

Images © Matteo de Mayda

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When the 13-story new Seoul City Hall was first unveiled in 2012, the curvaceous modern glass building sparked controversy for its incongruity in style with the former city hall, a preserved colonial-era stone structure that sits adjacent and has since been remodeled into a public library. In the following year, the city installed the enormous green wall in hopes of softening the glass-and-steel appearance and to reinforce the building’s environmentally friendly and energy-saving design.

Made up of cascading buckets of lush plants, the massive green wall serves as an indoor air filter that sucks in pollutants and fine dust. The vertical garden also helps save energy costs by regulating indoor temperatures and humidity levels. The City Hall’s additional energy-efficient features include the complex heat exchanger and pump system that meets nearly half of the building’s heating and cooling needs. Integrated photovoltaic rooftop panels provide 29% of the building’s energy through solar power. The perforated floors are heated with geothermal energy.

Related: Foliage Covered Botanical Building by Mass Studies

Nearly 7,000 triple-glazed, low-e glass panels clad the building and provide superior insulation to reduce heat loss while allowing solar gain. The building’s curvaceous silhouette, which is partly mirrored in the curved green walls, is both a nod to the eaves in traditional Korean architecture as well as an energy-efficient feature that helps mitigate solar heat gain. Click through Inhabitat’s Flickr Gallery to see more pictures of Seoul’s New City Hall.

+ iArc Architects

Images © Lucy Wang

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SHANGHAI, CHINA—(eSolarEnergyNews)—  JA Solar, one of the world’s largest manufacturers of high-performance solar power products, today announces that the rated power of its solar modules assembled by 60 multi-crystalline silicon («multi-Si») cells has reached a new milestone of above 280 W.

This newly achieved result, which has been independently confirmed and certified by TUV Rheinland of Germany’s Shanghai Testing Center, sets a record-high 17.2% conversion efficiency to date for the PV panels consisting of 60 regular industrial size (156×156 mm2) multi-Si cells and using a single standard junction box.

«This latest result of above 280W output power achieved from multi-Si modules with 60 cells is the continued effort of our RD follows JA Solar’s recently announced progress in reaching new efficiency record of multi-Si solar cells,» said Mr. Jian Xie, president of JA Solar. «This new milestone once again demonstrates JA Solar’s devotion in enabling cost-effectively manufacturing high-performance solar cells and modules to meet the growing demand for high-performance solar power products.»

«The output power of these record-setting solar modules we’ve just made can be further improved by fine tuning our module assembly process and encapsulation materials,» added by Mr. Yong Liu, Chief Operation Officer of JA Solar. «At least another five watts increase is definitely achievable. That will add significant value for our down-stream customers in terms of increasing power generation and reducing installation cost.»

ROSEVILLE, CA.—(eSolarEnergyNews)—Solar Power, Inc., a vertically-integrated photovoltai developer, today announced that its wholly owned subsidiary, SPI Solar Power (Suzhou) Co., Ltd. (“SPI Meitai”), has entered into a framework agreement with TBEA Xinjiang Sunoasis Co., Ltd. (“TBEA Sunoasis”), a subsidiary of TBEA Co., Ltd. (Shanghai: 600089) and a top machinery maker in China according to China Machinery Top 500 Research Report, to acquire from TBEA Sunoasis 168.5 megawatts (“MW”) of solar projects across China, including in Gansu Province, Xinjiang Region, Inner Mongolia Region and Qinghai Province. These projects are expected to be connected to the grid starting from 2014 to the end of 2015. SPI and TBEA Sunoasis will enter into a definitive equity interest purchase agreement no later than March 31, 2015, subject to the closing conditions set out in the framework agreement.

Mr. Jianxin Zhang, General Manager of TBEA Sunoasis, said, «We are very pleased to partner with SPI Solar in developing this prominent portfolio of solar projects. SPI has established itself as a premier developer of solar projects in China.”

Mr. Xiaofeng Peng, Chairman of SPI, added, “We are delighted to announce these agreements with TBEA Sunoasis, a leading provider of advanced solar products and system integration services. This important strategic partnership is part of an ongoing effort by SPI to take advantage of a rapidly expanding PV installation market across China through collaborations with key players.”

The LCOE calculation typically includes a variety of inputs, all of which are susceptible to the modelers experience and or bias for the future direction of the energy technology being modeled.  Typical inputs include: the cost of the installation (components, labor), financing costs, capacity factor, cost of OM, system production, and so on.  The strongest models use data from field experience (an actual system).  LCOE models based on systems that have been in the field for a number of years are the most robust, however, when the model is used to forecast the future, the bias of the modeler can and sometimes does insinuate itself into the results.

The major flaws of LCOE models are: 

1. The use of assumptions instead of data
2. Using data that supports the modeler’s goal (that is, assuming too low costs for hardware or OM) and too high production values
3. Adjusting model inputs to make a particular point
4. The assumption of that cost and price are synonymous

Concerning number 1, assumptions about the cost of components or financing (instead of data), using estimates for OM that are lower than the actual cost of OM, forecasting down from an assumption about cost that is already too low, assuming system production that is too high and assuming that the comparative energy technology will continue to increase in cost can lead to misleading results.   

Concerning number 2, it is not good practice to select the lowest available value and then forecast down from that point.

At this point, there are as many proprietary LCOE models as there are developers, manufacturers and consultants.  The word proprietary does not necessarily confer excellence on the model in question; all it does is state ownership of IP.  

When filled with hard data from systems operating in the field LCOE models can be good tools to observe trends overtime. The older an LCOE model gets (provided it is consistently updated with real data from an installation) the better it is as a tool for learning. Overtime such a model can become a superior forecasting tool as long as the modeler remains focused on developing an unbiased tool.

As a forecasting tool, LCOE models are highly vulnerable to bias. Types of bias include the belief that the cost or price of one energy source will continue to decrease and perhaps accelerate, while the cost or price of the competing energy source will continue to increase.  The behavior of prices for any good or service (including electricity) is variable, that is, prices do not typically increase or decrease in a straight line. LCOE models can be vulnerable to the belief of the modeler that prices for conventional energy will continue increasing while prices for solar generated electricity will continue decreasing. 

Assumptions are a form of bias. For example, the assumption that operations and maintenance costs (OM), which are currently undervalued, will continue decreasing from a point that is already too low, could insinuate bias into an LCOE model, leading to misleading results.

Mistakes in assumptions made around inputs such as the price of modules and other components institute bias.  Assuming that replacement parts will be inexpensive in the future adds bias.  Incorrect assumptions about the running life of a system or its production (output) add bias.  Developing blanket generalizations based on closely held beliefs adds bias. 

Unfortunately, LCOE models are highly vulnerable to manipulation to prove whatever point is the goal of the manipulator.  As a sales tool, these models can (and often are) adjusted to make an impression.  As a forecasting tool, these models can (and often are) adjusted to make a point.  Once bias and assumptions in place of data make their way into any model robustness and usefulness suffer and lessons are lost.

This is truly unfortunate because as deployment of solar continues, the industry needs all the learning it can get. The upfront cost of solar and the time to recover the investment should not be the point. Unlike conventional energy, once the hardware is installed the fuel for a solar installation is free and the system itself typically requires minimal maintenance depending on where the system is installed, size of the system, etc.  Use of solar has a significant role to play in the fight to save our climate, and it is far less expensive to install solar now than to fix (after the fact) the damage done to our environment due to climate change.   

Lead image: Thumbs up and down via Shutterstock

LOS ANGELES, CA—(eSolarEnergyNews)— 8minutenergy Renewables, LLC today announced the signing of a 25-year contract to sell 100 megawatts-ac (133 MW-dc) of clean, renewable solar energy from its Springbok Solar Farm project, located 70 miles north of Los Angeles in Kern County, Calif., to the Southern California Public Power Authority (SCPPA), on behalf of its participating member, the Los Angeles Department of Water and Power (LADWP). The transaction was conducted with 62SK 8me, LLC, a wholly-owned subsidiary of Calif.-based 8minutenergy Renewables, which is the nation’s leading independent solar PV developer. 8minutenergy will develop, build and operate the Springbok Solar Farm.

The Springbok Solar Farm project is a utility-scale solar generation facility sited on up to 950 acres of low-productivity farmland. Construction is projected to begin in the first quarter of 2015, with the site expected to be operational and delivering renewable energy to the LADWP by June, 2016. This clean solar generation plant will displace the equivalent of approximately 300,000 metric tons of carbon dioxide (CO2) per year, which is equal to the amount that roughly 12 million trees would displace annually.

«8minutenergy is pleased to work with SCPPA and LADWP to deliver clean renewable energy to the people of Los Angeles,» said Martin Hermann, chief executive officer of 8minutenergy Renewables. «We look forward to building the Springbok Solar Farm, which will produce approximately 265 million kilowatt hours (kWhs) of electricity annually for LADWP to power nearly 50,000 households in Los Angeles.»

“This project by 8minutenergy at Springbok is an important component of our Power System Resource Transformation program, and our efforts to further enhance solar as an energy resource for L.A.,» said Randy Howard, LADWP Power Assistant General Manager. “As Los Angeles expands its energy mix to include more renewables like solar, this contract with 8minutenergy will add capacity to the Barren Ridge renewable energy corridor and meet our goal of providing 33 percent clean energy to Los Angeles residents by the end of 2020.”

“SCPPA is pleased to be able to continue to assist our members in fulfilling the needs of their renewable portfolio,” said Bill Carnahan, Executive Director of SCPPA. “Through this engagement SCPPA looks forward to a successful and mutually beneficial business relationship with 8minutenergy.”

«8minutenergy appreciates the support this solar project has received from state, county and local officials,” said Tom Buttgenbach, president of 8minutenergy Renewables. “In addition, the Springbok solar project will benefit the region by creating 300 direct and 400 indirect jobs during construction. We are particularly proud that the workforce will include graduates from Homeboy Industry’s solar PV training program.»

Graduates of Los Angeles-based Homeboy Industries’ solar panel installation training and certification program will provide some of the labor for the projects through a partnership between 8minutenergy and the International Brotherhood of Electrical Workers (IBEW) Local 428. Homeboy Industries serves formerly high-risk, gang-involved men and women with a continuum of free services and programs, and operates seven job-training sites.

The solar power system for Springbok Solar Farm will be comprised of state-of-the-art solar photovoltaic modules, related power electronics, and other components including an advanced tracking system that follows the sun to maximize energy production. The PPA contract has been approved by the City of Los Angeles.