Marine baseload power
Combining geographically diverse tidal arrays to create a dependable minimum level of renewable generation, with additional tidal and wave power available above that baseload.
Predictable renewable power
Turning predictable tides into dependable power
Wind and solar are essential renewable technologies, but their short-term output is strongly influenced by changing weather conditions.
Tidal energy behaves differently. Tidal currents rise, fall and reverse, so generation from one location is not constant, but the timing of those changes can be predicted far in advance.
Pliosaur Energy's marine-baseload strategy is therefore not based on expecting one turbine or one tidal array to generate continuously.
The objective is to combine multiple arrays at locations with different tidal phases so that periods of lower generation at one location are supported by stronger generation elsewhere.
If sufficient phase diversity can be achieved, the combined portfolio can be designed around a minimum dependable level of generation. That dependable floor is the basis of the marine-baseload concept.
Geographic tidal diversity
The tide does not peak everywhere at the same time
The dominant semi-diurnal tidal cycle around the UK repeats approximately every 12 hours and 25 minutes.
However, high water, low water and the strongest tidal conditions do not occur simultaneously around the coastline.
The tidal wave moves around Britain and is influenced by coastline geometry, water depth and local hydrodynamic conditions.
This creates significant geographic differences in tidal phase.
These phase differences are fundamental to the marine-baseload strategy because they create the opportunity for generation from one array to overlap periods of lower generation at another.
Source: British Oceanographic Data Centre.
Multiple-array generation
Baseload is created by combining arrays
A single tidal array has a predictable but varying generation profile. As tidal currents weaken towards slack water, its electrical output falls.
An array at another location may be several hours out of phase and generating more strongly during the same period.
By developing multiple arrays with complementary tidal phases, their generating periods can overlap across the portfolio.
The objective is not simply to make tidal generation look smoother. It is to establish whether the combined arrays can maintain a minimum dependable output throughout the tidal cycle.
That minimum combined output can form the basis of a future baseload power commitment.
Portfolio-level generation
Individual outputs vary, but the portfolio is what matters
Each individual tidal array will move through periods of stronger generation and lower generation.
When appropriately phased arrays are combined, the output from one location can support another as its generation declines.
The important commercial measure is therefore not the minimum output from one array. It is the minimum combined output of the complete portfolio.
If that minimum can be maintained at a useful level, it creates the potential for a dependable block of renewable electricity to be contracted separately from the variable generation above it.
The longer tidal cycle
Tidal strength changes between spring and neap tides
Geographic phase diversity can address variation over the shorter tidal cycle, but the strength of the tidal resource also changes over a longer period.
Around new Moon and full Moon, the gravitational effects of the Moon and Sun reinforce one another, producing spring tides with larger tidal ranges and generally stronger currents.
Around the first and third quarter Moon, their effects partly oppose one another, producing neap tides with smaller tidal ranges and generally weaker currents.
The spring-to-neap-to-spring cycle takes approximately 14.8 days.
This means a commercial baseload level should not be designed around the high generation available during spring tides. It should be considered against the weaker conditions experienced around neap tides.
Bristol Channel example
Neap tides provide an important limiting condition
The Bristol Channel has an exceptionally large tidal range, making the difference between spring and neap conditions particularly noticeable.
At Hinkley Point, the published mean spring tidal range is approximately 10.7 metres, compared with approximately 4.8 metres during mean neap tides.
The mean spring tidal range is therefore more than twice the mean neap tidal range at this location.
Tidal-stream electrical generation does not vary directly with tidal range. Actual generation depends on local current velocity, turbine performance and operating conditions.
However, the spring-neap variation demonstrates why the neap-tide period is an important design condition when determining how much dependable power a future multi-array portfolio could commit.
Defining the baseload
Set the baseload at the dependable neap-tide level
The commercial objective is to develop enough geographically phase-diverse generating capacity that the portfolio maintains a useful minimum output even during weaker neap-tide conditions.
Once the arrays and their generating profiles have been modelled, the minimum dependable combined output during the limiting neap-tide period can be identified.
That level can provide the basis for the amount of electricity offered as marine baseload power.
The baseload commitment would therefore be set conservatively against the dependable lower part of the generation profile, rather than the average or maximum output of the arrays.
Anything generated above this baseload level remains additional renewable electricity.
Baseload plus additional generation
A dependable floor with generation above it
The baseload level does not represent the maximum output of the marine-energy portfolio.
As tidal conditions strengthen away from neap tides, the arrays can potentially generate increasing amounts of electricity above the baseload commitment.
During spring tides, this additional tidal generation could be substantially greater than the dependable baseload floor.
The future generating portfolio can therefore be considered as two different products: dependable baseload power and additional variable renewable generation.
Commercial value
Dependable renewable power can command greater value
Variable renewable electricity is commonly sold as it is produced. The buyer must therefore manage the difference between the generation profile and its own electricity requirements.
Baseload power is a different product. It provides an agreed level of electricity over defined periods rather than simply supplying whatever happens to be generated.
A dependable renewable-power commitment can therefore have greater value to an electricity purchaser and can create the potential for premium pricing compared with variable pay-as-produced electricity.
The generator also accepts greater responsibility when making a firm delivery commitment, so the baseload volume must be established conservatively and supported by robust resource and generation modelling.
For Pliosaur Energy, the commercial opportunity is therefore not simply to maximise annual electricity production. It is to maximise the amount of dependable, higher-value renewable power that can be supported by combining marine generation, geographic diversity and, where commercially practical, flexible electricity demand.
Extending the baseload opportunity
Flexible electricity demand can strengthen the baseload profile
The marine-baseload opportunity does not need to depend only on matching generation from different tidal arrays.
Pliosaur Energy could also work with large electricity users whose consumption can be shifted or temporarily reduced in response to predictable changes in tidal generation.
During periods when marine generation falls towards its minimum level, participating consumers could reduce or defer flexible electricity demand. When tidal and wave generation increases, that demand could be restored or increased.
This does not increase the electricity generated by the marine-energy portfolio. Instead, it reduces the amount of electricity that must be supplied during lower-output periods.
Combining phase-diverse marine generation with flexible third-party demand could therefore increase the amount of electricity that can be offered through a dependable baseload-style delivery profile.
Complementary marine resources
Wave energy provides additional generation opportunity
Pliosaur Energy's floating platform is designed to generate electricity from tidal streams, ocean waves, or both resources together.
The tidal portfolio provides the basis for establishing the dependable generation floor. Wave energy, which is driven by different physical processes, can provide additional renewable generation when conditions are suitable.
This additional resource can increase total energy production without needing to be relied upon when defining the tidal baseload commitment.
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Portfolio development
The right site is the site that strengthens the portfolio
The strongest tidal current is not necessarily the only consideration when selecting the next array.
Once marine baseload becomes the objective, a potential site must also be considered according to how its generation profile complements existing and planned arrays.
A location whose tidal phase fills a period of lower generation elsewhere could have significant system value even when another site has a stronger peak resource.
Important considerations therefore include tidal-current strength, tidal phase, spring-neap characteristics, wave resource, grid capacity, electrical demand, environmental constraints, navigation, installation, maintenance access and project economics.
The objective is to optimise not only how much electricity each array produces, but when it produces it.
A broader renewable mix
A different kind of renewable generation
Wind and solar will remain central to the transition towards renewable electricity. Marine energy can complement them with tidal generation whose timing can be predicted far in advance.
If a phase-diverse tidal portfolio can maintain a dependable minimum output through neap-tide conditions, it could provide firm renewable power alongside the additional electricity generated during stronger tides and suitable wave conditions.
Technical note
The baseload level must be demonstrated by modelling
The tidal-phase chart on this page uses historic tide-height data to demonstrate geographic differences in tidal timing. Tide height is not a direct measure of tidal-current velocity or turbine electrical output.
Establishing a commercial baseload commitment would require project-specific current measurements, hydrodynamic modelling, turbine performance data, array configuration, availability assumptions and electrical-network analysis across the full tidal and spring-neap cycles.
The figures and illustrations therefore explain the principles behind Pliosaur Energy's marine-baseload strategy and should not be interpreted as forecasts of future generation or contracted power volumes.
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