The Murgash peak area is located at Stara Planina Mountain. The site locates some 30 kilometers North- East from Sofia. The site elevation is at the highest 1687m i.e. Murgash peak and 1400-1500 meters at lower lying areas. The surrounding elevation at the foot of the mountains is approximately 600m. The wind energy potential of the Murgash peak looks promising on the basis of the existing measurement data. According to the readings of a manually read wind resistance anemometer, an average wind speed of around 8 meters per second on top of the Murgash Peak could be expected.

The proposed wind farm project is located in the mountain area of Stara Planina, about 50 km North-East of Sofia (see a map of Bulgaria in Figure 1), on the slopes of mountain Murgash. Latitude: 42.8° N, Longitude: 23.7° E.

OBJECTIVE

The objective of this work is to make an indicative analysis of wind conditions in areas surrounding Murgash peak based on available wind data. In the site area, there have been severe difficulties in carrying out the measurement campaigns which has caused the amount of available wind data is very limited. Meteorological modeling by Kjeller Vindteknikk AS and MCP (Measure-Correlate-Predict) method have been used in this project in order to increase the amount of available data.

2  BACKGROUND

Ecosource Energy is planning to build approximately a 500MW wind farm in areas surrounding the Murgash peak at Stara Planina Mountain. The site locates some 30 kilometers North-East of Sofia. The site elevation is at the highest 1687m i.e. Murgash peak and 1400-1500 meters at lower lying areas. The surrounding elevation at the foot of the mountains is approximately 600m. The present plan is to develop the wind farm in three phases. The first 100MW phase is planned to be built at areas where the site elevation is between 1450m and 1685m. The other two phases, 200MW each, will be built in areas where the elevation is lower compared to phase one.

Reliable wind measurements are needed from several locations for each phase as the terrain is complex in nature and stretches over an area of several square kilometers. There have been two measurement campaigns at the site, but all the measurement masts have collapsed after a short period of time due to heavy snow loads. The amount of available data varies from 2 weeks to 4 months in different masts. For wind assessments or feasibility studies, this data is insufficient, in general, at least one year of measurements is needed, but for project development purposes some indication of the wind conditions is needed already at this stage.

In order to increase the available data the meteorological wind modeling by Kjeller Vindteknikk and MCP (Measure-Correlate-Predict) method has been applied. Despite the efforts, the achieved results will be only indicative and include substantial uncertainties.

3  EXISTING WIND DATA

The wind data used in this analysis is from three different sources:

1. On-site measurements made with four 50m masts in 2007 in different locations in the site area
2. One-year modeled time series from Kjeller Vindteknikk AS
3. Wind data from the local meteorological mast at the Murgash peak

3.1  The on-site measurements made with four 50m masts in 2007

NexgenWind installed three 50m high measurement masts at the beginning of the 2007 in Murgash area. All three masts collapsed in February 2007. Later on, in 2007 three masts were installed again. A short review of the masts is presented in the following table and a map in which the masts are located can be found in Annex 1. Table 3-1 Review of on-site measurement masts

Wind measurement equipment was manufactured by Vector Instruments. Wind speed, wind direction, air temperature, and air pressure were measured from each mast. Wind speed was measured at heights 50m, 35m, and 20m, the wind direction was measured at 50m and 35m height, and temperature and air pressure at 4m height. Shafts of the anemometers were heated. This however was not sufficient to keep the instruments operational and readings reliable when the temperature fell below zero. The wind data was thoroughly checked and the erroneous data was removed. In the next picture (Fig 3-1) the available data is presented

As can be seen from the distributions the variations are great. The results from the masts M2 and M4 are the most unreliable because their measurement period is the shortest, only 2-3 weeks. In both cases, the wind directions seem to be only eastern. The measurement period in mast M4 is concurrent with the measurement period in mast M2. This also explains the reason why those two masts have similar results which however strongly differ from the other results. Due to wind variability over time a short measurement period may create a completely erroneous picture of wind conditions.

The complete measurement period with measurement masts M1 and M3 was approximately 3 months. In M1 wind data, the dominant wind direction is North-West whereas in M3 wind data it is North-East. The variation in the results is most likely caused by terrain topography. The northern winds around the Murgash peak at both sides. In complex terrain strong shifts of wind direction are common. This makes wind modeling using linear modeling tools such as WAsP unreliable.

The maximum measured wind speeds at Murgash peak during the measurement period are presented in Table 3-1. The highest peak wind speed of 27.7 m/s was reached.

Because of the very short measurement period, no conclusions can be made on maximum wind conditions. This issue needs to be monitored in future measurements.

Table 3-2. Maximum measured wind speed in 2007

The mean turbulence intensity was analyzed from the measurement data for wind speeds above 4 m/s and above 15 m/s at 50m height. The turbulence intensity remains moderate at all levels. At wind speeds over 4 m/s, which includes all the wind speeds when the turbine is in operation, the turbulence intensity is around 13% and at wind speeds over 15 m/s, which is the value used in the turbine IEC classification, the turbulence intensity is around 8%. According to these results, the turbulence intensity does not seem to be a critical issue on the site.

 Table 3-3. Measured turbulence intensity for wind speeds > 4m/s in 2007 Turbulence for winds >4 m/s in 2007

Table 3-4. Measured turbulence for wind speeds > 15m/s in 2007 Turbulence for winds >15 m/s in 2007

3.2 One-year modeled time series from Kjeller Vindteknikk AS

Kjeller Vindteknikk modeled wind conditions for the year 2007 in a 1km grid near the measurement mast M1 location. The model that was used in creating the computational data is a mesoscale model which is used in the preparation of weather forecasts globally. The coordinates of the nearest modeled point were 42°49,446N, 23°40,11E. Later on, this point will be referred to as MDL. The modeled wind speed and direction distributions at the MDL point at 60m height are presented in the following figure (Fig 3-6).

The modeled point is at rather steep ridge whereas the M1 is located on top of the same ridge. This will cause some differences in the results because the wind speed-up effect (wind speed speeds up when moving at higher elevation). The mean wind speed at the MDL point at 60m height is 6.6 m/s and the dominant wind direction is North-East.

3.3  Murgash Peak Meteorological station

Measurement data is available also from the Murgash Peak weather station. Wind speed has been measured with wind resistance anemometer that is read manually in every three hours. After removing the clearly erroneous data the results suggest average wind speed of 8.1 m/s for 2007. Dominating wind direction is north. The maximum recorded wind speed was 40m/s.

2  MODELLED AND CALCULATED WIND SPEEDS FOR DIFFERENT MASTS

The wind speeds were modeled with WAsP from every data point to all the mast locations in order to evaluate the wind conditions and modeling uncertainty. The results can be seen in the following table (Table 4-1).

In general, the variations are large. The difference between the highest and lowest values in each mast is 1.25-2.0 m/s. This size of errors in wind speed may tens of percent difference in production.

The estimated mean wind speed, which is calculated as an average from all the calculated results, is 7.2 m/s in M1, 8.0 m/s in M2, 7.1 m/s in M3 and 7.0m/s in M4 at 50m height. The highest variations in the results, and therefore also the greatest associated uncertainties, can be found on mast M2. The smallest variation is found on mast M1 which

is expected because it is the nearest measurement site to modeled data point (MDL) which is used in all the correlations and therefore in all the other data than in data from the meteorological station.

The modeled (MDL) 60m data gives clearly higher results than other data. WAsP has a tendency to overestimate the wind speed on top of the steep ridge. The same phenomenon, only in the opposite direction, can be seen in the results achieved using data from the meteorological station. The meteorological station is located on top of the ridge; again WAsP overestimates the speed-up effect, which causes an underestimation of the results at the measurement masts located at lower altitudes. In Annex 2, a wind speed map according to modeled 60m data is presented. This is most likely due to the calculation MDL point location in a steep ridge.

The highest mean wind speeds can be found on top of the ridge, 8-9 m/s at 50m height. The results for the other mast locations are close to one another. The mast M1 is located at a higher altitude than masts M3 and M4 but the Murgash ridge shadows later less in situations when the wind blows from North.

5  WIND TURBINES:

Ecosource Energy is planning to build approximately a 300 MW wind farm in areas surrounding the Murgash peak area at Stara Planina Mountain. The wind farm will be attached to the regional electricity grid and replace average fossil fuel based grid electricity generation.

The building of the Wind Power Park is planned to be done on several stages. When the project is completed, there will be built 150 turbines. For the aims of the project, Ecosource has bought 8700 decares of land.

The turbine supplier of the project is WinWind, Finland. Two types of wind turbines will be installed: WWD-1 (1MW) and WWD-3 (3MW). The company signed a contract with the supplier of the turbines for the supply and mounting of the machinery, with ABB Power Systems

/Germany and Bulgaria/ for development of systematic research of the Wind Park and a connection with the National Electric Base Net, with Poyry /Finland/ for analysis of the wind, a wind – measuring equipment and other consultative services, with Garrad Hassan /UK/ for analysis of the wind data.

Ecosource Energy Ltd. has completed the Bulgarian administrative procedure and has covered all legal requirements. List of available documentation: Land ownership documents with notarial attestation, Official acceptance from the Municipalities of the detailed country planning act, Approval from the Ministry of Environment and Water of the Environmental Impact Assessment Report, Resolution of Regional Environmental Inspection Agency, Resolution of the Ministry of Health, Resolution of the National Electricity Company for connection to the grid, Certificate from the regional Watering System Enterprise, Resolution of the local Water and Sewerage Enterprise, Resolution of the Regional Directorate of Agriculture and Forestry at the Ministry of Agriculture on the change of the land status, Planning visa, Support letters from local administration, JI documentation(JI Procedures Section)

Information about the turbines

WinWinD has developed an innovative wind turbine for the market with its WWD concept. WinWinD’s basic values include customer satisfaction and the operational reliability of the products, as well as the win-win cooperation achieved between the clients and WinWinD.

On the basis of thorough technical and economic research work the WWD concept, which allows electricity to be produced with a new innovative integrated power unit, was created. The basis for the design was efficiency, reliability, and ease of maintenance which allows the WWD concept to offer the most cost-effective production throughout its total life, combined with the lowest operating costs.