1. Future Offshore Wind Power
Systems
Beyond the Horizon

2. Contents
1. Introduction
2. Overview of Existing Technology
3. Deep water Wind Power Applications Using
Microgen Technology ltd Multiple Rotor Vertical
Axis Wind Turbine (MVAWT) systems
4. The Way Forward

3. 1. Introduction
The ongoing difficulty in producing and finding economical petroleum reserves and the need
to address the influence of climate change is moving to the forefront of national policy on
energy. It has been widely publicised and acknowledged that this presents a tremendous
growth opportunity for renewable energy developments and will eventually lead to a
proliferation of renewable energy systems competing with fossil, conventional renewable and
nuclear power generation. The UK is in a unique position to exploit the market for offshore
wind power as the resource is abundant onshore and offshore UK. However the UK
continental shelf does cover a large acreage of deep water particularly in locations where
offshore wind power is best exploited. The offshore acreage to the west of the UK presents
tremendous opportunities for the development and harnessing of wind energy. However any
offshore wind power installation has to meet a number of key criteria to be economically
viable:
i. Power output justifies significant capital investment
ii. Facilities are accessible for maintenance in a harsh environment
iii. Reliability and availability of installation has to be much higher than current
land based and near shore sites
The current design of wind power turbines utilised in large onshore and near shore wind
farms employs horizontal axis wind turbine (HAWT) generators and it is our view at
Microgen Technologies ltd (MGTL) that these designs have significant disadvantages for
what we would term ‘true’ offshore wind farms. We believe that there are significant
disadvantages in the HAWT design that requires alternatives:
i. Accessibility in far offshore locations
ii. Reliability may not be sufficient to make typical horizontal axis wind turbines
(HAWT) suitable for these environments.
iii. The HAWT wind turbine technology is reaching its size limit
The purpose of this document is primarily to describe the advantages of MGTL’s own design
for a multi-rotor vertical axis wind turbine (MVAWT) and to galvanise investment in the
concept to develop research in to the applicability of this design leading to eventually fund a
large scale prototype installation or demonstration unit in excess of 5 MW(e) capacity.

4. 2. Overview of Current Technology
This is a brief overview of the existing technology currently employed to date primarily
in the UKCS by way of example. However these models are applicable to similar marine
basin environments in other countries, e.g. Denmark.
2.1 Near Shore Windfarm Current Concepts
Figure 1 illustrates a typical example of what we would term the first generation in
offshore wind turbines. The turbines are mounted offshore (in fact near shore) in
relatively shallow water with the turbine tower situated on a monopod structure fixed to
the sea bed. The monopod structure design severely limits the water depth that these units
can operate in to a maximum of about 20 m. These are not true offshore windfarms in the
sense that one would expect to see in the round 3 licence awards in the UK and the
monopod support structure employed in this design limits them to coastal locations.
However these developments have allowed wind power development to free itself of
many of the planning obstacles in onshore locations and the coastal location allows for
more unobstructed wind patterns. However they still present planning issues in terms of
visual impact from shore for example and while they are free of land they still do not
capture all of the wind energy that could be available further offshore.
2.2 Deepwater Offshore Windfarm Current Concepts e.g. Beatrice
Offshore Wind Farm
The Beatrice wind farm is an excellent model for how far offshore wind farms could in
fact look and probably the best illustration of how far the current HAWT design can be
employed in this type of situation. The wind turbine tower is mounted on a jacket
structure (Figure 2) which is very similar to those employed in offshore oil and gas
developments and the water depth that these systems can operate in is only limited by the
capital cost of the jacket and its impact on the project NPV. The Beatrice wind farm was a
significant development in offshore wind technology and what we would view as the
intermediate step toward a true offshore windfarm development concept. This
development proved that a large traditional HAWT machine can be transported and
installed offshore with a conventional jacket type structure to provide a stable operating
platform using offshore oil and gas construction technology to execute the installation of
the facilities. This is in essence the birth of the second generation of offshore wind
turbines where true deepwater application has been translated in to a commercial
demonstrator reality. It is not unreasonable to expect to see this type of unit being viewed
as a potential de facto standard for far offshore wind turbine developments. However they
could have access limitations for far offshore locations and may become limited by the

5. size of wind turbines that could be available. Therefore there are two potential key
parameter issues in these units:
i. Availability impacted by access difficulties
&
ii. Power output limited by physical size of the turbines
This is where we at Microgen Technologies ltd see the design of wind turbine becoming
important and likely to spawn concepts other than the traditional three bladed HAWT as
alternatives to be located far offshore.
2.3 The Next Generation
As stated earlier our view at MGTL is that at this point in time no one truly completely
understands or has an appropriate model for how a far offshore location wind farm would
look other than an extrapolation of the Beatrice wind farm concept. The model in most
potential developer’s minds is of future deepwater wind farm development employing
jacket type support structures. Some Norwegian concept developers have put forward
floating anchored or guyed buoyant support structures as a possibility, again supporting a
HAWT three blade configuration.
However this model could prove to have limitations in a number of areas:
i. Can the turbines be sufficiently large to be feasible and justify the high capital
costs of such a project?
ii. Can long term reliability be assured for these units operating in a hostile far
offshore location?
iii. Can these wind turbines be safely accessed by air using helicopters?
iv. Vessel offshore access systems would be useless for most of the year?
v. Are blades reaching their size limit?
There are therefore a number of issues that need to be resolved before a commercially viable
offshore windfarm development in one of the round 3 licence areas can feasibly be
considered. It is our view in Microgen Technologies ltd that the supporting structures
required to support the wind turbine can use existing technologies e.g.
i. Fixed piled to sea bed jacket structures
ii. Guyed buoyant monopods

6. iii. Other floating structures, e.g. a lightweight dual hull anchored
semisubmersible
Where we differ from the current views of the industry is that for the larger size of wind
turbine that would be required in deepwater locations we believe that vertical axis wind
turbines can have a part to play. We are also of the view that some of the limitations of this
design can be overcome and make it feasible for far offshore deepwater applications. The
MVAWT concept has a number of features that make it advantageous in comparison to
HAWT. Figures 1 to 3 illustrate schematically and to proportionate scale how the evolution
from a near shore mono pod based HAWT to the MVAWT concept developed by Microgen
Technologies ltd would look.
Figure 1 Coastal/Near shore
Monopod Type Structure
Figure 2 Deepwater Jacket Type
Structure Supporting a HAWT

7. Illustrated in figure 3 is a multi rotor vertical axis wind turbine (MVAWT) where the rotors
rotate around a vertical axis. In the case illustrated in figure 3 four rotors rotate around the
support tower, each rotor drives an individual generator located within the tower and the
tower is in essence the vertical axis of rotation in this design. Loads are balanced across the
tower structure by the rotors contra-rotating to each other. As can be seen from this simplified
illustration the size of facility will match the hub height for a HAWT mounted unit
employing similarly sized rotor blades. The sheer size of the offshore located MVAWT (and
current HAWTs) makes it feasible to mount the generators inside the support structure and
allow reasonable access for maintenance and repair personnel. As can be seen from figure 3
helicopter access is unrestricted by the wind turbine blades and this allows any size of aircraft
to operate and service the windfarm and meet the requirements of CAP 437 easily. As will be
discussed in the next section we view unrestricted helicopter access for long range helicopters
a key success factor that is required to allow operation of far offshore located wind turbines.
However ease of access alone is not sufficient motivation to consider an alternative to
HAWT technology and it is also the case that this concept was conceived to provide a
significantly higher power output for a given hub height for a comparably sized HAWT.

8. .
Figure 3 Far Offshore Located
Unit Incorporating Multi Rotor
Vertical Axis Wind Turbine
Figure 2 Deepwater Jacket
Type Structure Supporting a
HAWT
Comparison of MVAWT and HAWT Turbines Located
on Deepwater Jacket Structures

9. 3. Deepwater Wind Power Applications Using Microgen
Technology ltd Systems MVAWT Technology
3.1 Overview
In 2008 MGTL identified the concept for a multiple rotor vertical axis wind turbine
(MVAWT) for far offshore locations as it was our belief that, although the output from
current designs of horizontal axis wind turbines was and is becoming more efficient there
are alternatives that may have been overlooked. This view is based on the premise that
current HAWT designs require significant spacing in arrays and to increase output the
wind turbine becomes increasingly large. The use of ever larger rotors requires
increasingly larger structures to support the wind turbine and in offshore locations
helicopter access may become more difficult and create aviation safety issues, particularly
in far offshore locations where a Eurocopter EC 225 or similar size aircraft would be
required on grounds of crew size and particularly range to facilitate a maintenance visit
for even the most basic maintenance tasks, e.g. addressing a sensor failures or condition
monitoring.
In our design the rotor rotates around the vertical support structure and multiple rotors
can be mounted on the structure in a stacked configuration preferably with the rotors
contra rotating to each other. The contra rotating rotors both balance torsional loads
across the structure and can reduce spacing requirements between turbine installations in
an array. The vertical support structure employed in this design of turbine is virtually
identical to the ‘pole’ type structure to support a HAWT nacelle and hub. On an
individual rotor basis when compared to a similarly sized HAWT the individual rotor on
the MVAWT is naturally less efficient, however we believe that the efficiency could be
certainly 35-50% on a P90 to P50 basis and potentially up to 70% of the power output of
a similarly sized HAWT rotor at the P10 range with correct design of blades. We believe
that there is value in research funding to develop knowledge of this range in equipment
performance evaluation and sizing.
The MVAWT proposed design utilises a four blade rotor, this ensures that the wind
turbine will always have a uniform force distribution across it and that it will not stall
through sub optimal attitude to the oncoming airstream. The configurations we would
expect to be employed on an offshore location would typically involve four or six rotors
each driving an individually coupled generator unit to each rotor. The generators would
be mounted within the ‘pole’ type vertical support structure with the final drive
connecting to the wind turbine rotor via openings in the structure wall to allow the gear
meshing. The MVAWT unit can be mounted on a wide variety of offshore structures
either fixed jackets or floating structures that have been proposed for conventional

10. horizontal axis wind turbines by a number of companies involved in wind turbine
manufacture and general offshore engineering.
For far offshore locations the economic penalty of extra blade and generator costs can be
easily absorbed into the overall cost as the offshore installation and support structure
construction make up a sizeable portion of the project capital costs.
We also believe that the through life costs through increased availability of the MVAWT
concept versus a HAWT unit makes it much more economically attractive when the
availability is modelled on a probabilistic basis.
3.2. Principles of Operation
The MVAWT system presents a highly efficient large scale power generation system for
use in offshore environments. The system operates in a mode where the blades utilise
both drag and lift forces to provide motive force to a coupled generator in a constant
rotational cycle. If one considers how a wind speed anemometer behaves then each rotor
in the MVAWT behaves similarly but much more efficiently as it utilises lift forces in
combination with drag forces as opposed to an anemometer which is purely an inefficient
drag device.
3.2.1 Rotor Design
The rotor consists of a four bladed design where the blades are connected to a central
rotor hub via a blade root hub. The blade material an root construction being almost
identical to current HAWT technology.
The blades auto pitch in to the wind with predominant drag force application applied
when the blade is moving along with the wind direction, this is when the blade is being
acted upon and transmitting torque to the generator via the gear drive. As the blade
approaches the oncoming wind in the opposite direction the blade is lifted by the lift
forces applied by the oncoming airstream and the blade acts like the wing of an aircraft in
level flight and produces minimal resistance to the diametrically opposite blade being
pushed on by the wind and in fact this blade acts like the wing of an aircraft during take-
off in terms of its aerodynamic resistance and performance.
As referred to in earlier sections the minimum efficiency is 35% upwards compared to a
HAWT rotor this is because over 135°of the rotational cycle the blades are acted on
positively by the oncoming airstream directly driving the rotor. Whilst we say this
efficiency is a minimum of 35% however we believe this can be greater due to the higher
torque applied to the generator through the blade also acting like a large lever and the
force vectors being more complex as forces are also transmitted and captured down the

11. length of the blade as well as across it in a HAWT being a purely crossflow device.
Therefore for a large diameter HAWT compared to a 4 rotor MVAWT of the same or
similar hub height we would expect a power output some 40% greater than the HAWT
unit as a minimum.
On an individual rotor basis this type of wind turbine can never compete with a HAWT.
However for the same hub height in an HAWT more MVAWT rotors can be
accommodated. This is particularly of value in exposed offshore locations where the
foundation and platform are of considerable expense and limit the size of HAWT and
hence power output achievable.
3.3 Reliability
The MVAWT has a number of key components omitted that are key requirements in a
HAWT design, namely:
Nacelle: The generators and drive train are all completely contained within the
cylindrical steel support structure. Therefore there is no need for a nacelle as
employed on HAWT designs.
Yaw Drive: The MVAWT does not need yaw control or correction as it is optimal
whatever the wind direction as it presents a uniform profile around its vertical axis to
the oncoming airstream.

12. Pitch control: No direct pitch control mechanism is required. However a driven pitch
adjustment mechanism can be employed for parking the blades by moving them to a
neutral pitch angle, say in situations where wind speed is too high.
Multiple generators may be viewed as potentially presenting a reliability issue, however
in fact this configuration acts in the opposite fashion. As an analogue one could think of a
single versus multiple engine aircraft, therefore if one unit fails reduced overall system
performance can still be maintained from the units that remain online. When looking at a
single HAWT if one component where to fail the entire unit would be offline. In the
MVAWT unit should a rotor and generator combination sub unit have a failure the other
units rotating around the main structure will continue to operate effectively. This means in
effect that should a single generator unit shut down within the MVAWT configuration
only 16-25% capacity would be lost either in a six or four rotor configuration.
3.4 Offshore Access
For a wind turbine to be mounted in a far deepwater offshore location it would have to be
serviced by maintenance personnel transported to the site either by helicopter or a vessel.
Both of these options are discussed in the context of the MGTL design and its advantages
over a HAWT unit.

13. 3.4.1. Helicopter Access
Where helicopters service an offshore location it is essential that the helideck must be
clear of obstructions for aircraft approach and landing on the helideck area. A large
HAWT wind turbine blade when in rotational state may not allow a helicopter to make a
landing approach due to the air turbulence created by the blades and further complicate
the aircraft approach by its impact on the ambient wind direction. It is therefore likely
that even if a helicopter was able to make a landing that the wind turbine would have to
be stopped and confirmed stopped before the aircraft could land in most cases. Reference
to CAP 437 for helicopter operations on offshore wind turbines current requires this for
helicopters dropping of crew by winch. Additionally the blade of a large turbine can
present a variable obstruction to a helideck mounted on a wind turbine nacelle. The
MGTL view that it is best to completely remove the hazard and this was a key rationale in
the MVAWT concept. For helicopter access to a large offshore HAWT wind turbine, a
helideck of sufficient size could be mounted, but this would add significant weight to the
nacelle and requirements of the yaw drive to slew the hub and nacelle in yaw correction.
The MGTL design of stacked rotors rotating around a vertical axis allows a helideck to be
mounted at a safe distance above the rotors. This configuration allows a helicopter to land
a crew onboard the installation while the wind turbine remains on operation if it is a
routine maintenance visit involving running checks on the wind turbine generators.
Additionally this configuration also presents a uniform obstruction location that is
mounted well below the approach flight path to the installation helideck. The rotors
mounted below the helidecks on the MVAWT units allows a helicopter to approach the
wind farm at a height in excess of any of the helidecks and whatever MVAWT unit is
being landed in the windfarm the flight and landing approach will not need to take into
account any other installations.
For a given size we expect that the MGTL design will give a significantly lower overall
structure height for a given power generation capacity and not much greater if at all than
for the hub height of a HAWT installation employing similar sized rotors. The reduced
structure height offers significant advantages when considering installation, visit strategy
and general operations in a far offshore deepwater location. Further design detail
refinement of the MVAWT unit also allows for adequate structure projection marking
lights to alert passing aircraft.

14. 3.4.2 Vessel Access
Access to any offshore structure in a far offshore location requires a specialist vessel with
dynamic positioning capability similar to North Sea platform support vessels. However
the transfer of personnel from vessel to an installation is fraught with difficulty and it is
only recently that access systems involving motion compensated booms and bridges
mounted on a platform supply mono hull vessel have become available. However even
these systems have limitations that do not offer anywhere close to the availability of
helicopter operations for transferring personnel to and from an offshore installation. Sea
state limitations defined usually by significant wave height currently limit these system
operations to around 2-2.5m excluding current/swell direction in relation to the structure
being serviced. Additionally for far offshore locations the sailing times to these
windfarms would require the maintenance crew to reside on the support vessel. This is
not a barrier to this type of support operation but it does give rise to the need for servicing
crews to work rotational cycles similar to those on an offshore oil and gas installation. If
maintenance crews were offshore resident it would require a highly mobile twin hull
semisubmersible vessel with dynamic positioning capability that is far superior to vessels
currently available. Vessel access from sea to either a horizontal or vertical axis wind
turbine would be similar and therefore no particular advantage is offered by any particular
wind turbine configuration in this regard.
The economics of a vessel that is capable of operating in deepwater far offshore locations
may be prohibitive when compared to helicopter operations as a means of support,
particularly for routine maintenance visits and light repairs to equipment that could cause
a shutdown, e.g. instrumentation and hydraulics.
It is therefore clear that helicopter access offers significant advantages in servicing a far
offshore windfarm. However it may be feasible to have in addition to helicopter access a
highly capable field support vessel incorporating the capabilities of a twin hull
semisubmersible and excellent dynamic positioning capability, e.g. DP 2/3 dynamic
positioning capability. The vessel could be employed for maintenance support activities
that could not be serviced by a helicopter based crew. Such a vessel could also act as an
infield based service and accommodation vessel and support helicopter transits within the
winfarm and from the shore base for transfer of personnel. However even if a vessel
could become economically viable as a windfarm support infrastructure, it is highly likely
that helicopter access would still be pivotal to the success of any windfarm operation.
The MVAWT offers a significant access advantage for helicopters in providing an
unrestricted helideck access and uniform flight path in the windfarm at all altitudes for
approach to helidecks located within it. This feature allows instrumented landing

15. approaches to be possible in weather states where helicopter access to HAWT wind farms
is not possible.
4 The Way Forward
In the UK with imminent energy deficiency and ever increasing costs of carbon emissions
the case for far offshore deepwater wind power developments has never been more
compelling. However the industry appears to be in a state of limbo waiting on the next
big event to happen in wind power development. It is our view that the industry is in a rut
and constrained with development models incorporating the conventional three bladed
HAWT scaled up to the point where it becomes impracticable. Alternatively there are a
number of ill conceived vertical axis wind turbine concepts that have been conceived with
a lack of knowledge of the harshness of the offshore operating model or basic
understanding of reliability concepts, not to mention the ability to realistically scale these
up. These words may seem harsh however the industry needs to react to the challenge and
this has to be delivered by a technically robust alternative.
We obviously as the concept developer of the MVAWT unit believe it to be the best
prospect as an alternative model for large scale offshore wind power developments using
ever larger HAWT technology. We cannot guarantee at this stage that this concept is the
ultimate solution however we firmly believe it to be worthy of development on the
following compelling grounds:
i. The blades will utilise existing technology within the maximum size range
already deployed in HAWT technology
ii.Multiple generators on a single offshore structure will offer improved overall
online uptime
iii.The weather dictated access issues related to HAWT designs do not apply to
MVAWT
iv.For a given offshore location utilising the same number of support structures
the power output will be higher
v.A number of HAWT key components can be eliminated, principally yaw drive
and pitch control, thus availability and reliability can be increased

16. At Microgen Technologies ltd we believe that there is a compelling case to develop the
MVAWT technology and prove the concept on an industrial scale for a number of
commercial reasons in addition to the technical issues cited above and these commercial
advantages are:
i. Development time can be swift due to readily available component technology
in the market place
ii. This is a suitable product for a new entrant to renewable energy systems
iii. For an offshore location the project NPV would be expected to be favourable
on the basis of higher power output and uptime for little extra capital cost for a
given structure size and load out tonnage.
The concept development through to commercial scale is depicted in the attached plan.

17. Activity Detail Timeline Enablers
Concept
Engineering
University
Research Project
Mid 2015-2016 Funding from
appropriate body
to allow University
selection
Small Scale
Prototype Build
Early 2016 Prototype funded
from same grant
as University
research funding.
Onshore Prototype
(250-500 kW)
Site selection
and test body
selection
Early-Mid 2017 Requires
significant funding,
up to 10 million
Euros
Selection of
turbine builder
Mid 2017-Early
2018
Turbine builder
may contribute
partly to funding
for intellectual
property rights
transfer
Design, build
and construct
Mid-late 2018
Test and
evaluation
Late 2018-end
2019
Full season of
data, preferably
compared to
similar size HAWT
unit in same
location.
Offshore Prototype
(2-5 MW)
Design, build
and construct
Late 2019 through
to beginning 2020
Significant funding
required to allow
this project to be
commenced. Initial
estimate 50 million
Euros

18. Activity Detail Timeline Enablers
Offshore Prototype
(2-5 MW)
Installation
engineering and
execution
Engineering 2020
Execution early
summer 2021
Funded from same
monies to design
build and construct
Test and
evaluation
summer 2021 to
Summer 2022
Gain a full offshore
season of test data
to allow economic
evaluation of full
scale unit and
incorporate
lessons learned on
reliability and
design in to final
design.
An operational
budget of 2 million
Euros will be
required to support
test and evaluation
phase.
Type approval (5-10
MW)
Incorporation of
lessons learned
from offshore
prototype to final
design
2023 Requires
manufacturer to
accept the concept
and assume all
intellectual
property rights and
to self fund full
scale product
development.