Wind Farm Feasibility Study and Site Layout Design
Starton Engineering JSCo. entering the wind energy market by developing a portfolio of wind farms. Through a strategic search Starton Engineering JSCo. identified a series of sites for potential wind farm development in Bulgaria and several neighbor countries. For increasing of wind power production of big wind farm is proposed jet blade VAWT s fixed on small towers between the bigger HAWT turbine. As an example of JET BLADE VAWT see the video here.

Starton Engineering JSCo. provides technical and environmental services to progress the priority sites, including a feasibility study for a large site in mountainous and coastal regions. The viability of the site was known to be dependent on the realistic capacity of the wind farm, due to a major cost anticipated in relation to the required Starton Engineering JSCo. provided an initial estimate of potential wind farm capacity at the site, followed by an in-depth study, which determined the feasible number and location of turbines. This was achieved by investigating the technical and environmental constraints experienced at the site and by developing an appropriate wind farm design in response to the specific features of this site and surroundings.

Our team gave consideration to priority issues, including:

State stimulus for wind power plants in Bulgaria

Power engineering is the fastest progressing branch of the world energetics in the last years, and it is due to a lot of reasons. Most important of them are; rise in the price of energy in general; increasing of the global warming and ecological problems with thermoelectric end atomic power stations, which dominate in the world energetics, increasing of the capacity of wind power generators, and not at the last place – reduction of the prices of the wind power generators on a world scale, toward their level ten years ago. On the background of the described global tendency, the energy policy of our government is completely in unison with the european tendencies for economy and administrative stimulations of energy production from renewable energy sources (RES). The preferential purchase price, for example, of the electricity from RES, in particular from wind, defined from The Commission of energy and water regulation, raised from 6 eurocents per kilowatt-hour in 2003 to nearly 9 eurocents per kilowatt-hour in 2006. Namely the permanent and methodical examination of the euro-energy policy guarantee, that in our state, energy productions from RES will progress ahead of time.

At these profitable preferential legal and economic conditions, the wind climate in more regions in Bulgaria already allows building of effective wind power stations, which are profitable, and at the same time provide not long term of recovery of the investments.

In the colloquial language, and in the meteorology as well, the velocity of the wind is accepted as parallel vectors to each other, square to the terrain, which vectors has changeable at all azimuths direction. But in the reality such wind doesn’t exist; furthermore at the frontier layer of air.

Differential wind energy audit
Generally said, the vector of the wind is not horizontal. Its horizontal ingredient is this one, which has the energy importance for the operation of wind generators. But it is part of the wind speed, which has components along the other two axes of the three-dimensional Cartesian (3-D) space as well, and these components hinder more or less the work of the wind turbines.

The results of this measurement are being analyzed individually as components, and in common.
First goal is sifting out the important energy ingredients of wind from the other – not useful, which the turbines drug along, and evaluation of the damages. These damages do not depend only on the not horizontal compounds but on the amplitude fluctuations of the wind at all directions, called turbulence, as well.

Designing of wind power plants
At the wind power stations, the primary energy resource (the wind) is variable at its velocity and its direction. Therefore the designing of wind power stations always divides into two consecutive phases. The first one is the wind energy audit, and the second one is the designing itself. Both phases are even important. First phase is decisive for the choice of transformation technology of the wind energy into electricity, which has important meaning for the optimal choice between competitive wind power generators.
At the second phase are being chosen alternative variants (alternatives) of wind power generators, on the base of analysis of their technical parameters of energy and their best correspondence with the specific wind climate conditions of the audited place.
The project concludes with a technical and economical analysis, investments and ecological evaluations of the projected alternative versions.

Detailed plan within three steps, of preliminary engineering, is presented below:

Stage 1.  WIND ENERGY AUDIT OF TERRAINS

1. Calculation of energy density of the wind currents
1.1. Identification of the terrains
1.2. Profile of the landscape
1.3 . Influences of wind climate over the operation of the wind power aggregates
1.3.1. Influences of the climate specifics
1.3.2. Influences of the wind dynamic on the work of the wind turbines
1.3.3. Analysis of the results of 3D-measurements
1.3.3.1. Analysis of the turbulence
1.3.3.2. Differential analysis of the wind energy, used for driving wind aggregate
1.3.3.3. Transformation of the important wind energy into electricity, according to the parameters of wind aggregates
1.3.3.3.1. Aerodynamic losses of wind energy
1.3.3.3.2. Mechanical and electromagnetic losses
1.4. Diagrams of speed frequencies of the wind at directions for the chosen places
1.5. Wind-dynamic and analytic modeling
1.5.1. Initial parameters for wind-dynamic modeling
1.5.1.1. Authentic year of measurement
1.5.1.2. Correlating wind-dynamic modeling
1.5.1.4. Correlated wind statistic
1.6. Results of the mean density of the wind energy stream
1.6.1. Calculating method.
1.6.2. Results of the density of the wind energy stream
1.6.3. Results of the density with energy importance, of the wind energy stream
1.6.4. Expected deviations of the measurements and the results

Stage 2. CHOOSING OF OPTIMAL WIND AGGREGATES FOR THE TERRAINS, ACCORDING TO THE ENERGO-TECHNICAL CRITERIA

2. Determination of the technical parameters of the wind power generators, in accordance with the results of wind energy audit
2.1. Fixing the places of foundation of the wind power generators
2.2. Aerodynamic specifics
2.3. Alternatives for the height of the supporting post
2.4. Alternatives for rotors
2.5. Alternatives for transmission and electro generation
2.5.1. Transmissions
2.5.2. Generations and supporting of standard parameters of the electricity
2.5.3. Connecting
2.5.4. Innovative fundamental points
2.5.5. Offer for proper alternatives for the concrete project
2.6. Pessimistic, optimistic and realistic evaluation of the annual production of electricity for the chosen alternatives of generators
2.6.1. Absolute potential of the annual production of electricity
2.6.1.1. Determination of the average annual operating hours of the wind aggregates
2.6.1.2. Determination of the actual prevailing wind velocity
2.6.2. Actual annual production of electricity
2.7. Graphic analysis of the capacity and the efficiency of the wind aggregates
2.8. Parallel between the capacity and the efficiency of the chosen wind aggregates

Stage 3. TECHNICAL AND ECONOMICAL ANALYSIS OF THE INVESTMENT EVALUATION OF THE CHOSEN ALTERNATIVE PROJECTS
3. Investment and economical evaluations of the appropriate versions
3.1. Size of investment
3.2. Financial incomings
3.3. Risks and discount percent
3.4. Operational expenses
3.5. Investment cycle
3.6. Period of recovering of the investment
3.7. Net present value of the investment
3.8. Internal norm of profitableness
3.9. Correlation incomes/expenses
3.10. Cost price of the electricity production
3.11. Comparison of the alternatives
3.12. Results of ecological investigation
3.12.1. Ecological evaluation
3.12.2. Ecologically-economical evaluation
3.12.3. Conclusion of the investigation
Final conclusions and recommendations

Not technical criteria of wind power farm design
In principle, each project has energy-technical and economical part. Here we will mark formal and economical criteria, which have essential place in the complete engineering. It is inexpediently for these questions to be considered in details in one book, because each detailed analysis is concrete. Such analyses are being made individually for each wind energy project.
We should mind at firs place, that the choice of over all dimensions and consequently the capacity of the turbines depends on the terrain and on the way of using it. There are two formal restrictions, in accordance with special regulation, where the distances between the turbines and between them and the urbanized territories, are defined (they exist in project as well). Distances between 5 to 7 turbine rotors at the direction of the prevailing wind for the concrete terrain are standardized and 3 to 5 diameters – square to this direction. This is criterion, which provides relatively good work of a group of turbines, but it doesn’t guarantee neither their optimal production of electricity, nor their optimal reliability and durability. For evaluation of these characteristics, it is necessary to be made configurational project, which is subject of the second part of this book, whose first edition was published in 2005.

The second formal criterion is the sanitary norm that is determined in a minimum -600 meter from the frontiers of the urbanized territories. Without making detailed comment, we should note that the closeness to transmission line with proper tension and free capacity to export generated electricity from the wind power station also has importance at the engineering stage. If there isn't existing proper electric infrastructure, the time for putting the project into operation will be shortest.

Prices of power generated by wind turbines (feed-in tariff)

Since the beginning of 2007, there are two stage preferential tariff for buying up of the electricity, generated by new wind turbines,

* For wind generators with 2250 (more than 0.257 capacity factor ) and more full effective operational hours annually - 80 euros / MWh
* For wind generators with less than 2250 (below 0.257 capacity factor ) full effective operational hours annually - 90 euros / MWh

The above tariffs are without VAT. As new wind generators are considered turbines, produced later than 01.01.2006. Wind generators, produced before this date, are considered as old, no matter if they are exploited or not.

From the table we can see that the differences are quite big and they will have significant influence over the investment indexes, as well as on the size of the needed opening stock.

Even without making such analyses, one can see that it is economically profitable the turbines to work less than 2250 hours, in comparison with the case, when they would have worked a little bit more than this hour limit This refers to new machines. If they are not big, their transport and their montage will be not expensive and in the long run it could be turned out that they are economically more effective over terrains, where the wind conditions are more unfavorabl. But If the machines are cheap (second hand) and proper aggregates are being mounted on windy places the, than their economical efficiency could be better in comparison with the new machines, no matter that the buying up tariff is considerably lower.

This brief analysis gives us the possibility to understand, that universal proper choice of aggregates doesn’t exist. They can be small or big; new or old; horizontally-axial or vertically-axial; individually working, or a few in a big group – wind park; or in few smaller groups etc. All reciprocally excluding alternatives mentioned here, can be combined in different ways. But providing for the height of the generators over the terrain and their initial expenses, the problem appears with ambiguitive solution.

The tariffs above will be subject of increase, because according to the Energy Law, they may not be lower than 70% of the end price of electricity for the home consumers.

Designing of innovative wind turbines

In large numbers one can see the propeller wind turbines. They work optimally, when the horizontal component of the complex vector of the wind is parallel to their rotor shaft. That’s why these turbines are being frequently called horizontally axial HAWT. The basic disadvantage of HAWT is that their rotor always revolves not only around its horizontal shaft, but it also moves at 360 angular degrees at the azimuth. This necessity complicates the structure of the entire turbine, and make it more expensive, furthermore if considering that the rotor is posed high above the terrain and the mechanical forces from the pressure of the wind as well as the bending moments they create, are considerable, which impose the rotors to be mounted on solid and massive supporting towers and respectively fundaments. All these problems can be avoided, if the wind turbines are constructed in such way, that is not necessary the revolving of the rotors around two mutually perpendicular axles, but only around one – the axle of their rotor shaft. Such machines are constructed, most frequently, with vertical rotor shafts and their blades turn around vertical axle. They are being called vertically axial machines or VAWT.VAWT are relatively simple in their structure and have significant advantage, that their center of gravity is low, close to the terrain, in contrast to the center of gravity of HAWT. For that reason the forces and the bending moments over their supporting construction, are vastly reduced. After all said till now, naturally appears the question why the horizontal axial propeller machines are much more distributed in practice than the vertical axial turbines.

The answer of the question, in brief, comes from the fact that the blades of propeller machines are loaded only from one side – the side of the wind pressure direction, and that’s because the rotor always revolves so, that the wind is parallel to its shaft. From mechanical, dynamical and kinematical point of view, the unilateral load over the blades is more advantageous, and therefore the rotors of HAWT are much more lighter and can rotate with higher revolutions, because the centrifugal forces in them are smaller. For each revolution of the vertical axial machine, its blades pass through two positions, in which they are loaded bilaterally consecutively. Such librating load over the blades for each revolution is a reason for them to be made robust, respectively heavy, the centrifugal forces are being got big and the rotors, as a whole, revolve unstable, particularly at high revolutions. And the energy effectiveness at transformation of the kinetic energy of the wind into useful work, when revolving the shaft of the turbine, strongly increases with the rise of the revolutions. Therefore, even if in principle, two prime kinds of turbines have a nearly even theoretical effectiveness, the limitation of the rise of revolutions of the vertical axial turbines, make their real energy effectiveness lower.
 

However, in contradiction from the horizontally axial turbines, which are unstable in not horizontal and turbulent wind flows, the vertically axial turbines are slightly sensitive in not horizontal and turbulent wind flows; furthermore they are considerably more noiseless. The last two characteristics make them applicable also for populated places, where the wind flows are turbulent, and where the noise during their operation time is unallowable.

Cybernetic system for wind farm control - Patent pending

Vertical and horizontal wind shears, yaw misalignment and/or turbulence act together to produce asymmetric loading across a wind turbine rotor. The resultant load produces bending moments in the blades that are reacted through the blades, hub and low-speed shaft. The amount of blade’s deflection is measured using one or more sensors placed on the turbine tower. The output signals from the sensors are used to determine the magnitude of the resultant rotor load. This information is used to effect the blade pitch change needed to reduce the load and thereby reduce fatigue and loading on various turbine components.