NOT ALL “GENERATION + STORAGE” SYSTEMS DO THE SAME THING.
The distinction matters. Some projects combine two separate assets. Some storage machines use one reversible powertrain to charge and discharge. Heat pumps use electricity to move additional energy from an external thermal source. ESWave is designed around a different proposition again: one physical asset can either harvest external renewable energy or absorb and store electricity according to what the energy system needs.
TWO FUNCTIONS. OFTEN TWO MACHINES.
A wind farm plus a battery, a solar plant plus storage, or another hybrid project can balance supply and demand by combining a generator with a storage asset. The functions coexist at project level, but each machine remains specialised.
Generator
Harvests an external resource such as wind, solar, waves or tides.
Storage
Absorbs electricity, shifts it in time and returns part of it later.
Balancing
The project can serve both sides of the grid — but normally by using two distinct assets.
A MOTOR/GENERATOR CAN PRODUCE ELECTRICITY WITHOUT CREATING NET ENERGY.
Pumped-storage hydro and regenerative electric-drive systems illustrate a second category. During charging, electricity is converted into stored mechanical or gravitational energy. During discharge, the same or a related machine converts that stored energy back into electricity.
Charge
Electricity → motor/pump → stored energy.
Discharge
Stored energy → turbine/impeller/generator → electricity.
THE HEAT PUMP SHOWS WHY OUTPUT CAN EXCEED ELECTRICAL INPUT WITHOUT CREATING ENERGY.
A heat pump is an important comparator because its useful heat output can be several times the electricity supplied. The reason is simple: electricity powers the process, while additional heat is transferred from an external thermal reservoir.
COP = useful heat / electrical input
Qout = Welectric + Qsource
A COP of 5 can therefore mean roughly 100 units of electricity plus about 400 units of ambient/source heat becoming 500 units of useful heat delivered.
What it is not
It is not 500 units of electricity generated from 100. COP measures useful thermal transfer, not electrical generation efficiency.
THIS IS THE HFED QUESTION.
TWEFDA’s proposition is not simply to package a generator and a battery together. ESWave is intended to let one physical machine select between two complementary energy functions through a common architecture and PTO.
POWER REQUIRED → GENERATE
Same asset
The generation and storage functionality are not two separate commercial machines bolted together.
Opposite grid conditions
Generation and storage respond beneficially to opposite system needs.
Selective operation
The useful question is not “can it do both?” but “can it do the function the system requires now?”
ROUND-TRIP EFFICIENCY AND SYSTEM ENERGY RETURN ARE NOT THE SAME METRIC.
The heat-pump analogy helps here. A passive storage path cannot create energy, but a storage cycle can coexist with generation from an external renewable resource.
Stored-energy path
Erecovered = η × Echarge
For the storage component, η remains the appropriate round-trip efficiency and losses must remain visible.
External-resource contribution
Esystem out = Erecovered + Etidal + Ewave …
If additional output is harvested from tides or waves, that is new generation from an external resource — not storage efficiency above 100%.
The Bay of Fundy is an extreme illustration: tidal ranges can approach 16 metres. That can make the tidal contribution potentially very significant, but any claim such as 100 electrical units eventually contributing to 500 units of electrical output must remain a modelled scenario until effective head, displaced mass, buoyancy, timing and losses are quantified.
AFTER STORAGE IS DEPLETED, THE ENERGY STORY CAN CONTINUE.
A conventional battery that reaches its lower state of charge must wait for energy to recharge it. ESWave is conceived differently. Once the storage function is exhausted and the machine returns to the sea, it can change role and harvest wave energy as a point absorber. The source of that subsequent electricity is the ocean, not the previous charge.
GENERATION CAN BEGIN.
ESWAVE COMPETES ON BOTH SIDES OF BALANCE — BUT NOT AT THE SAME TIME.
When the system values incremental supply, ESWave competes with generators, imports and other sources of flexibility. When the system has excess power, it competes with batteries, pumped storage, demand response, interconnectors and curtailment avoidance. Its strategic advantage is therefore not simply “more generation” or “better storage”; it is higher usefulness of one asset across opposite grid conditions.
MW, MWh, LCOE, LCOS, ROUND-TRIP EFFICIENCY AND COP MEASURE DIFFERENT THINGS.
A generator is judged by power and energy production. Storage is judged by capacity, duration and recovery efficiency. A heat pump is judged by useful thermal output relative to work input. An HFED crosses categories, so one conventional metric can hide much of its value.
Generation
MW · MWh/year · capacity factor · LCOE · availability.
Storage
MW in/out · MWh capacity · duration · round-trip efficiency · LCOS.
Heat pump
COP · SCOP · useful thermal energy · source temperature.
HFED / system
Mode availability · switching time · bidirectional power envelope · annual asset utilisation · flexibility revenue · external-resource contribution.
THE TWEFDA ASSOCIATION POOLS POWER BEFORE FINAL ELECTRICAL CONVERSION.
In the current reference concept, six ESWaves do not each carry an electrical generator. Three generators are located in the common TWEFDA Hub.
CAPEX
Three shared generator sets instead of six device-local sets reduce duplicated high-value equipment.
OPEX
Fewer generators mean fewer machines to inspect, service and overhaul.
Part-load strategy
High sea states can use all three generators; low aggregate power can be pooled through one while the others remain idle.
Moving-mass strategy
ESWaves remain lighter when rising because they do not carry the generator; during descent, gravity and Weight-Changing Energy can make additional weight useful.
FOUR QUESTIONS FOR EVERY “HYBRID” TECHNOLOGY.
1 · How many assets?
Two specialised machines or one common architecture?
2 · Where does output come from?
New external resource, stored energy, or transferred ambient energy?
3 · Can function change on demand?
Can the same asset select the response the grid needs now?
4 · Where is conversion hardware?
One generator per device, or pooled conversion in a common plant?
In TWEFDA’s 2025 Business Plan, Ocean Hydro Omni / HydroWind was identified as the closest comparator for placing generation and storage within one frame. The key distinction TWEFDA wants to test is whether ESWave can go further by making the OR itself controllable while the Association also centralises final power conversion.
THE HOME STORY NOW HAS A TECHNICAL AND ECONOMIC BACKBONE.
Balance → Generation OR Storage → external resource accounting → shared generation → lower duplication → higher asset usefulness.
