WITH THE RECENT SURGE IN FOSSIL FUEL AND GAS PRICES - in pursuit of more cost-effective energy resources the energy sector focus has turned towards other, more sustainable forms of generation such as solar PV and wind energy innovation. Naturally this, in addition to the worldwide goal to minimize the effects of carbon dioxide emissions and reach carbon neutrality, have led to the rapidly increasing demand for renewable generation.

Why wind?

For hundreds of years people have tried to obtain the energy contained in the wind – first automatic wind turbine dates back to 1887 (Figure 1). The concept is not new and wind generation is used in many places (specifically the Scandinavian countries) in large and medium scale applications to provide green energy to meet the consumers’ needs. However, one area where wind generation has been overlooked is small-scale application. While solar (PV) generation, especially in recent years, has experienced the limelight in terms of subsidies and media promotion, small-scale wind has not had the same luck (attention). Therefore, with soaring electricity prices, this technology could present untapped potential for residential generation.

Figure 1 Blyth's windmill design, from his patent

The study

The main goal of the small-scale wind economic analysis was to evaluate the impact elevation and consequently wind profile has on energy generation and economical parameters. In order to evaluate the small-scale wind generation potential, the difference between electricity expenditures when wind turbine is used and when all demand is supplied by the electrical grid is calculated. Yearly production was calculated using hourly wind speed measurements for the years of 2018 and 2021 for two vertical (3,6 kW and 6 kW) and two horizontal (2,3 kW and 1,4 kW) wind turbines. It was assumed that vertical wind turbines are installed in cities, on top of apartment buildings and horizontal wind turbines are used in residential suburb areas, next to private houses. Therefore, appropriate 4 apartment (for vertical WT) and 4 house consumption measurements (for horizontal WT) were used when calculating yearly electricity expenses. Wind speed was measured at 10m elevation and as with height wind speed increases, thus, it was recalculated for each height using logarithmic approximation.

During the calculations, two different Nord pool electricity prices were evaluated: 2021 03 – 2022 03 average 111 Eur/MWh price and the average 2021 electricity price of 94 Eur/MWh. With surging electricity prices it is estimated that the economic analysis of small-scale wind would present even better results. Although, even in an unsubsidized case which is presented below the results are promising.

Findings

Having conducted the calculations for different scenarios, it was found that in cities, between the heights of 17,5 and 50 meters, 3,6 kW vertical turbine has the better pay back period, when comparing the results to 6 kW vertical turbine. The results can be seen in Figure 2.

Figure 2 Payback period dependency on height for vertical 3,6 kW and 6 kW wind turbines

Whereas for horizontal wind turbines, it can be seen in Figure 3, that the more powerful 2,3 kW turbine presented better pay back period than 1,4 kW turbine in the heights between 9 and 22 meters. 

Figure 3 Payback period dependency on height for horizontal 2,3 kW and 1,4 kW wind turbines

Having looked at the hourly wind speed data, it could be seen that 2021 presented to be a year with very high wind speeds. Consequently, the calculated wind turbine generation was significantly higher than in 2018. Yearly generation at 10 meters of 3,6 kW vertical turbine in Klaipėda in 2021 was 3904 kWh which is 1,38 times more than the 2821 kWh generated in 2018. The differences in the 3,6 kW generation over the different years are presented in Figure 4.

Figure 4 Annual 3,6 kW vertical wind turbine generation in Klaipėda for 2018 (left) and 2021 (right) (kWh)

Summary

Small-scale wind economic analysis highly depends on the accuracy of the wind speed measurements at the place of the wind turbine installation. For its accurate development potential evaluation, wind speed measurements at these locations should be carried out. From the analysis it can be summarized, that wind speed and uniformity have the biggest influence on the small-scale wind turbine payback period. In addition to that, electricity price and the ratio between initial investment and the wind turbine power also influences the economic analysis results. Wind turbine power should be chosen such, that the amount of energy it generates would be as close to the amount of energy the user consumes. The calculation results indicate that the highest potential for small-scale wind generation can be seen in building horizontal wind turbines next to private houses in suburbs or next to country houses. The hybrid installations of solar and wind generation in conjunction with energy storage and their viable benefits should be further investigated and identified. One clear advantage of this hybrid system is the smaller seasonality influence as solar generation is more prominent in the summertime while wind generation – in the wintertime.

Prepared by Ignitis Innovation Hub - Saulė Gudžiūtė