What to do with a 20kW turbine looking out on the Irish sea in Kirkcolm?

West Wind looking out over the Irish Sea

Figure 1 Westwind turbine install at Knockneen Croft

Setting the scene

On a trip over to Scotland to commission a 100kW off-grid Turbine with EMMA two of the senior members of the Cool Power Products team got a call on the ferry mid way across the Irish Sea. The man on the other end of the phone was in a bit of a quandary about how to get a 20kW wind turbine up and running with a grid connection. Never shy of a challenge the CPP team said they would help and by coincidence drove straight from the Ferry to his house to assess what could be done en-route to their other site.

Export limit to zero or a £1million line upgrade.

After observing the site, the turbine and the house, CPP concluded that the EMMA would be a valuable addition to the site for heating as well as secure a grid connection. The EMMA would serve the important purpose of allowing the connection of the turbine to the already saturated grid without having to pay an upgrade cost of £1000000 as it would limit the export to the DNO’s requested zero export. A CPP representative liaised with Scottish Power to help get a connection agreement for this site by using an EMMA with Export Control and detailing how it would serve its function on this particular site.

As the site is incredibly windy during the winter the house would get cold due to the drafts of the frequent storms. The turbine would produce the most power when it would be needed most but would only be a good fit if the EMMA system was there to harness it properly.

By installing an EMMA with Export Control (EC) the house would save on its oil bills and still receive its FIT tariffs from its new turbine. Using the EMMA with EC was also the most economical way to get connected to the grid and avoid costly line upgrades which has been an attribute of the EMMA system with UK network operators.

System design

Cool Power Products worked with the client to agree on a proposed two tank system. The primary tank would supply the house and the secondary tank would supply heating to a workshop and log drier. It was agreed that an EMMA with a capacity to supply 8 no. 3kW immersions would be required to satisfy the DNO zero export and reduce the heating bills for the house as much as possible.

The owner set about getting the plumbing done and installed a timber shed on the outside gable of the house where the Oil boiler flow and return entered the building. Because of size constraints 3 smaller cylinders with a combined capacity of 1000L were installed with a stratification system to maintain equal heat across all three cylinders.

Figure 2 Panoramic of 3 cylinder heating system.

The cylinder system

There are three stat’s on this cylinder system:

Stat 1. CPP advised to use a stat in conjunction with a switchover valve to prioritise the cylinders for heating the house when they were above the required temperature. If the stat is disengaged the OFCH will be used to directly heat the house and not the cylinders.

Stat 2. The stratification pump only kicks in if any of the cylinders reach c40’C. This is to keep equal heat in all cylinders and to keep the immersions from tripping out on over temperature. It is important to keep all the immersions online to allow the EMMA to dissipate full power if required. The importance of this is twofold, while maximising the heating capacity is one benefit, if immersions drop out on over temperature then there is a risk that EMMA won’t have sufficient load to match the output and thus maintain the export limit. If this happens the EMMA will disengage the turbine from the grid.

Stat 3. This stat controls a switchover mechanism in the EMMA cabinet. It enables the EMMA to switchover its load diversion from the three tanks to an alternative tank in the workshop. The stat is placed on the stratification pump pipe work and is set at a high temperature so that the rads get very hot water. Once the threshold temperature is met the EMMA switches over to heating the alternative bespoke tank which is 4000L in size. This tank is used for heating the workshop on site and providing heat to a wood log drier. When the temperature in the primary tank drops below the stat threshold, the heating will switch back to the primary tank.

The EMMA installation

RBB Electrical who are a trained EMMA with EC and West Wind installer were nominated to carry out the install as they would be commissioning the turbine. RBB are also PV installers and are an experienced G59 relay fabrication and commissioning company.

Anders Howard and Tim Crook from RBB Electrical carried out the electrical install of the turbine and the EMMA unit.  

RBB ran the output cable from their G59 cut off in the workshop to a Henley block in the house where the mains came in. The Henley block split the power into mains incoming, HouseHold mains to fuseboard, and Micro Generation Mains output from the turbine allowing the CT’s to correctly monitor the power.

An experienced wind turbine member of the Cool Power Products Team that had worked on the project from the beginning went over to assist in the commissioning of the system. This was to help provide an overview on how the system worked and to display the live data from the EMMA data logger to the clients so they could understand exactly what everything was doing. It also allowed Cool Power Products to install and use their remote logging facility to observe the turbine from Ireland.

The second cabinet in from the left in Figure 4 shows the EMMA SP15/120 with EC enclosure supplied and built by Cool Power Products.

EMMA Data Logger helps people see the EMMA at work in real time

The EMMA data logger is a useful tool that demonstrates what is happening on a graph in real time. The Client was quite impressed to see the turbine production being exactly matched with demand by EMMA when production went above the normal household loads. Over time during the day the temperature was observed climbing by about 10 degrees in light winds. This was confirmation that the system was going to work as intended in the heavy winter winds and provide a very successful heating solution for the house.

On the date of commissioning there was a steady light breeze which allowed us to demonstrate EMMA doing her thing!

Figure 5. EMMA tracking load to output and keeping a stable voltage

80 milli-second PID adaptive tracking algorithm in action

The points indicated in the data log above show the effectiveness of the EMMA GVS (Grid Voltage Stabilisation) function. Where the turbine production oscillates between 0 and 4kW’s above the background demand, the voltage is maintained as a steady flat line. Where the production is less than the demand and EMMA has nothing to manage the voltage dips under load.

The logs where the green and red lines overlap show the output and the demand matching perfectly. This only happens when there is exportable production. The exportable production is sent to tank heating.

What is Grid Voltage Stabilisation?

 Grid voltage stabilization on an EMMA is maintenance of a steady grid voltage when there is exportable production.  This is a unique attribute of the EMMA system where it has the ability to keep the demand matching the output to maintain the voltage within the settings of the inverters.

Why is it important?

If the Grid voltage goes above the upper limit of the inverter on this turbine the inverter will fault and disconnect from the grid. The EMMA will prevent this from happening as long as the loads it controls are available. The importance of this is as follows:

  1. It keeps the turbine online and making power for FIT payments.
  2. It keeps the tank warm and oil bills low.
  3. It reduces wear and tear of the turbine in free wheel mode and therefore prolongs the life of the machine.
  4. If inverters are switching in and out frequently an observable flicker can be observed in the lighting of the dwelling which is not just annoying but can be attributed to epileptic fits.
  5. An unloaded turbine is significantly louder than a loaded turbine and while the West Wind has its own RPM governing plant, like other turbines it is louder when the inverters are not loading it.
  6. It maintains a stable grid and quiet turbine for the neighbours also.

Summary

As lots of wind turbines are installed to gain from FIT tariffs throughout the highlands and lowlands in Scotland and indeed the UK in general, in many instances there is a perfect fit for an EMMA to reduce heating bills while in a lot of cases increasing the FIT payments by keeping the turbines online. The Knockneen Croft turbine is certainly an example of how the present and future of renewable small wind should be.

Turbine: Westwind 20kW with peak output of 24kW’s. (Now Ampair - http://www.ampair.com/)

DNO: Scottish Power (SPEN).

Installer: RBB Electrical - http://www.rbbelectrical.co.uk/

EMMA Type: SP15/120 with Export Control max diversion 24kW (1 x PWM and 7 SSR Control). Supplied by www.coolpowerproducts.com

Customer: Very Warm and Very Happy J

 

 

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