Cost Saving with Small Wind Turbines

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Small wind turbines have a high potential to be part of a decentralized renewable energy system. Though costs are high and profitability is still low. For several years now the small wind industry has been expected to reach a tipping point with an increase in sales volume and a drop in production costs. This assumption is being analyzed in this paper and further saving potentials in small wind turbine production costs are outlined. Based on small wind market reports in several countries a global market analysis for small wind turbines in the range of 1 kW to 5 kW has been performed. From the findings a relevant set of manufacturers have been selected to study manufacturing methods and development trends.

The global market segment has a size of 22 000 small wind turbines annually with China, the United States and Great Britain as leading countries. The sales of market leaders can be estimated to be between 1000 and 2000 units a year. For the main components potential future cost savings are being discussed.

The tower is found to be the part with the major saving potentials. Measures to lower production and installation cost include centrifugal casted, segmented fiberglass towers and slip-joint techniques to connect the tower segments.

This article focuses on grid-tied systems with capacities from 1 kW up to 5 kW rated power and takes on the U.S. Small Wind Industry Road map's thesis that the industry “is close to the ‘tipping point’ where production volumes would skyrocket, causing production costs to plummet”. There is a lot of empirical evidence proving further high expectations on imminent production and sales increase such as a “huge potential” and an “age for the industry to boom and prosper“ or an potential annual energy yield of 1.5 TWh for Great-Britain. However, the expectations on plummeting production costs need to be backed by specific measures in design, manufacturing, logistics or installation cost.

Present prices for small wind turbines range from 2300 €/kW to 4600 €/kW compared to about 1000 €/kW in large wind . Amortization of investments without state subsidies is only viable in off-grid applications and on sites with high wind yields. The objective of this poster is to presents cost saving potentials of small wind turbines.

Blades: Savings of about 70% with change to large scale industrial processes such as matched metal molding, pultrusion or RTM-Molding, DLR has developed a filament winding process for small wind blades manufacturing at an industrial scale which has not been put into practice so far.

Generator: Production costs for permanent magnet generators are made up to 70% of material with rare earth elements prices being the main cost driver. Fixed cost degression is possible though it only has limited effect on the overall price.

Bearings: Early small wind turbines used bearings with additional bearing flanges in their machine housing. These flanges were casted and machined parts and drove costs up. Present bearing concepts have integrated the bearings into the housing and thereby cut costs by approximately two thirds.

Tower: The tower is the component with the main effect on the overall price of the small wind system. Manufacturing choices concern raw material, joining processes and surface protection. Furthermore the tower design and quality has effects on installation, logistic and life cycle cost.

Tower design using new structure materials is under development and has large potential to reduce cost. Significant cost savings can come from centrifugal casted, segmented fiberglass tower and slip-joining concepts for the tower segments.

Controller and inverter: Inverter technology is largely derived from photo-voltaic applications and costs are estimated at 0.50 €/W [9]. Therefore small wind inverter technology benefits from manufacturing and R&D investments that have been driven by the larger PV industry and will continue to do so.

Logistics: To facilitate shipment and work sharing in international value chains worldwide the length and width of a 20' sea freight container as an international standard should be met. 

The article that production costs may plummet has been partly proven right. The large cost potentials by industrial composites manufacturing processes for rotor blades have been realized by a few large small wind and component manufacturers in the 1-kW- to 5-kW segment with annual production volumes near 1000 units. Further cost savings have been realized by improved bearing concepts in turbine design and by benefiting from R&D efforts on inverter by the PV-industry.

After all annual sales volume is a limiting factor for smaller companies to invest in cost cutting technologies. Future potentials will come from innovations in tower design and manufacturing technology.