Hours on the clock

Marine Current Turbines have now racked up 1000 hours of export to the National Grid, as reported here.

MCT claims an average capacity factor of 66% for the period of operation. We have calculated a capacity factor, based on ROC register figures, which shows a steady(ish) increase to around 25% in November 2009. This calculated CF does not make any allowance for downtime, availability of marine mammal onservers, or (crucially for MCT) the limitations imposed by daylight-only working.

Since daylight in November is less than 50% of the time, and the trend is upwards, we can see that a claimed 66% capacity factor in December could be realistic.

If true, it's excellent news for the company and the technology, as it's always all about cost per MWhr, and more MWhrs means a better metric.

More interesting marine recruitment

Interesting to see that Atlantis Resources is beefing up its management team too, with the hiring of Jim Forbes as Chairman of the UK business.

Details here.

So just like Aquamarine, there's a real strengthening of management teams going on in the space right now, and a real commercial focus on the new hires.

Aquamarine recruitment

Did anyone else notice that Aquamarine just recruited Richard Round, former FD and briefly MD of Novera as their new Finance Director?

This should strenghthen their fund raising capacity and demonstrates a new level of seriousness in the marine space.

Exciting!



Apologies for brevity - posted from my iPhone

UK 3rd Offshore Wind Round

32.2 GW of potential new capacity has been identified under the Crown Estate's programme. From the Crown Estate website:

The developers who have signed exclusivity zone agreements are:

1. Moray Firth zone, Moray Offshore Renewables Ltd which is 75% owned by EDP Renovaveis and 25% owned by SeaEnergy Renewables – 1.3 GW

2. Firth of Forth zone, SeaGreen Wind Energy Ltd equally owned by SSE Renewables and Fluor – 3.5 GW

3. Dogger Bank zone, the Forewind Consortium equally owned by each of SSE Renewables, RWE Npower Renewables, Statoil and Statkraft – 9 GW

4. Hornsea zone, Siemens Project Ventures and Mainstream Renewable Power, a consortium equally owned by Mainstream Renewable Power and Siemens Project Ventures and involving Hochtief Construction – 4 GW

5. Norfolk Bank zone, East Anglia Offshore Wind Ltd equally owned by Scottish Power Renewables and Vattenfall Vindkraft – 7.2 GW

6. Hastings zone, Eon Climate and Renewables UK – 0.6 GW

7. West of Isle of Wight zone, Eneco New Energy – 0.9 GW

8. Bristol Channel zone, RWE Npower Renewables, the UK subsidiary of RWE Innogy – 1.5 GW

9. Irish Sea zone, Centrica Renewable Energy and involving RES Group – 4.2 GW


The clear winners, as shown in the graph above, are the big 6 utilities (except for Eon and especially EdF who are complete absent), plus Vattenfall, which is increasingly becoming a member of the big 6.

MCT power curve - analysis

MCT has just published a power curve for its Seagen device in Strangford Narrows (see figure above and link here). The curve shows a period of output at the design capacity of 1.2 MW, in what is described as a “medium tide”. This tide appears to have peaked at 3.1 m/s, which may be medium for Strangford, but is pretty impressive for most sites.

We realised that it’s possible to drill into this curve to come up with some (very) theoretical ideas of the capacity factor which might be achieved by the technology. First we constructed a velocity lookup table by taking a ruler to the graph, which shows the power output (kW) at various stream speeds (m/s).

m/s - Power
0 - 0
1 - 20
1.25 - 100
1.5 - 180
1.75 - 400
2 - 600
2.25 - 900
2.4 - 1200

We then constructed a model which characterises a simplified tidal environment, with stream speed varying according to a diurnal cycle (sinusoidal variation over 24 hours, in 2 flood, 2 ebb tides) and a 28 day lunar cycle (again simple sinusoidal variation).

We entered a maximum stream speed (peak rate achieved at spring tide) and a minimum stream speed (peak rate achieved at neap tide) and constructed a lookup on an hour by hour basis to estimate the power output over a month.

Based on a maximum stream speed of 3.2 m/s and a minimum stream speed of 1.6 m/s (ie neap maximum is half as fast as spring maximum), we find that the average theoretical power output (assuming no outages) to be 450 kW, making the capacity factor 38%.

The model shows that output is sensitive to both maximum stream speed and the ratio between spring and neap peak rates. The table below shows the relationship between capacity factor and the maximum stream speed) assuming that neaps are limited to 50% of the maximum stream speed in springs. The month-average capacity factor for various maximum spring stream speeds is:

m/s - CF (%)
2.8 - 28%
3 - 34%
3.2 - 38%
3.5 - 45%
4 - 53%
The table below shows how the capacity factor is influenced by the ratio between the maximum neap speed and the maximum spring speed based on a maximum spring stream speed of 3.2 m/s. The table shows maximum neap speed and month-average capacity factor.

m/s - CF (%)
0.8 - 31%
1.2 - 33%
1.6 - 38%
2.1 - 45%
2.4 - 48%

All of these power output estimates are wildly theoretical – and should be treated with extreme caution. Next we’re going to combine this power curve with some actual tidal data from tidal diamonds on charts to see how that looks.