Having quantified the “red stack” of consumption and defined a necessary reduction strategy for transport and heating, we know that the future sustainable society requires meeting an electrical demand of 48 kWh/d per person (120 GW nationally), representing nearly a tripling of current UK delivered electricity consumption. If this plan is to be technically feasible and not a “pipedream,” we must now rigorously calculate the production side—the “green stack”—to determine how much energy Britain can realistically generate from its own renewable resources.

The current energy debate is often riddled with “twaddle” and relies on broad adjectives, such as claiming “we have a huge amount of wave and wind.” The numerical truth, however, illustrates just how challenging replacing fossil fuels will be. We must quantify exactly how “huge” our resource potential is compared to our consumption.

The inescapable conclusion derived from the arithmetic is stark: while Britain’s technical renewable potential is vast, the sheer scale of deployment required—often involving the industrialization of country-sized areas of land and sea—means that current lifestyle cannot be sustained solely on UK renewables, largely due to public opposition (the “wall of no”).

1. Wind Power: The Scale of Industrialization Required

Wind is often championed as Britain’s best resource, given the country’s high wind speeds. However, converting this resource into meaningful electrical output demands an enormous, country-wide physical commitment.

Onshore Wind: The 20 kWh/d/p Ceiling

The potential power output of wind farms is estimated by multiplying the power generated per unit land-area by the area available per person.

For a typical wind speed of 6 meters per second (13 mph), the average power output of a wind farm is estimated at 2 W/m². Applying this density to the land area available yields a theoretical maximum potential.

Onshore wind limit: 20 kWh/d/p—requires 50× Denmark’s wind capacity

This figure immediately highlights the monumental scale needed to make a difference: this single component of the green stack alone must provide nearly half of our estimated future electrical demand of 48 kWh/d/p.

To put 20 kWh/d/p into perspective, achieving this requires a deployment equivalent to:

  • 50 times the entire existing wind hardware of Denmark
  • 7 times all the wind farms of Germany
  • Double the entire fleet of all wind turbines in the world (at the time the sources were written)

Offshore Wind: Two Waleses of Turbines

Offshore wind benefits from stronger and steadier winds than onshore, leading to a higher average power per unit area, estimated at 3 W/m² (a 50% increase over the onshore estimate).

Offshore wind potential: 48 kWh/d/p from shallow waters covering two Waleses

The area required for these installations is massive:

  • Shallow offshore: Within British territorial waters, the shallow area (depth less than 25–30 meters) covers approximately 40,000 km², an area roughly equivalent to two Waleses. Occupying this entire area would theoretically generate 48 kWh/d per person.
  • Deep offshore: Deep offshore wind is currently not considered economically feasible, but could theoretically add another 16 kWh/d per person.

To achieve the full 16 kWh/d/p from shallow water alone, one would need to fill a 4 km-wide strip of turbines all the way around Britain’s 3,000 km coastline.

2. Hydroelectric and Marine Energy (Tide and Wave)

While marine resources often sound powerful, their contribution, particularly in the UK, is limited by physics, geography, and current technological efficiency.

Hydroelectricity

Hydroelectric power requires both altitude and sufficient rainfall. The maximum theoretical potential is derived from calculating the gravitational power of all the rain running down to sea level.

  • Theoretical limit: About 7 kWh/d/p nationally
  • Plausible practical limit: Allowing for losses and practicality, the realistic sustainable contribution from hydroelectricity is estimated to be 1.5 kWh/d per person

This target still represents a seven-fold increase over the UK’s current hydropower output of 0.2 kWh/d per person.

Tidal Power (Barrages and Streams)

The UK, surrounded by seas with strong tides (a form of lunar energy), has a significant resource.

1. Tidal barrages (Severn): The proposed Severn barrage, generating power on the ebb tide alone, is estimated to contribute 0.8 kWh/d per person on average.

2. Tidal stream farms: These use “underwater windmills.” The total extractable power from tidal stream farms in the UK is estimated to be 9 kWh/d per person.

The total plausible technical output from maximized tidal energy (barrages plus stream) is around 10 kWh/d/p.

Wave Power

Waves are created by wind and contain potential and kinetic energy. The average wave power in the Atlantic is significant, around 40 kW per meter of wave front.

  • Device efficiency: While some devices have been projected to deliver 19 kW/m, real-world systems have suffered enormous losses. The LIMPET on Islay achieved only 5% of the predicted output.
  • Plausible contribution: The maximum contribution of wave power is conservatively estimated at around 2 kWh/d per person.

3. Solar Energy and Geothermal

Solar and geothermal resources, though perpetually available, face constraints of land area, population density, and thermal limits in the UK context.

Solar Thermal (Heat)

Solar thermal panels use sunlight to directly heat water. This process is highly efficient at capturing the sun’s energy.

  • Output: Installing panels on a south-facing roof area of 10 m² per person could deliver approximately 13 kWh/d per person of thermal energy.
  • Role in plan: The future consumption plan incorporates a realistic contribution of 1 kWh/d per person from solar hot water.

Solar Photovoltaics (PV) (Electricity)

PV panels convert sunlight directly into electricity. In the UK, average sunlight power density is low.

  • Output: Assuming high-efficiency panels (20% efficient), a rooftop area of 10 m² per person would only yield about 5 kWh/d per person of electrical energy.
  • The power vs. efficiency confusion: While PV panels are becoming cheaper, efficiency must not be confused with delivered power, which remains limited by the density of solar radiation in the UK.

Geothermal Power

Sustainable geothermal energy relies on the natural heat flow from the earth’s interior.

  • Sustainable limit: Because the UK population density is high, attempting to extract heat for sustainable electricity generation yields a maximum of only 2 kWh/d per person.

4. Biomass and Waste (The Food vs. Fuel Conflict)

Biomass, including energy crops, wood, and agricultural waste, supplies chemical energy. However, its potential is severely limited by the efficiency of photosynthesis and the competition for arable land required for food.

  • Physical upper bound: Photosynthesis in the most efficient European plants achieves about 2% efficiency, yielding 0.5 W/m² of chemical power.
  • Land constraint: The UK has approximately 2800 m² of agricultural land per person. If all of this land were dedicated to energy crops, the gross chemical energy generated would be 36 kWh/d per person.
  • Net potential: After factoring in inevitable energy losses during harvesting and processing, the true maximum potential power from biomass is estimated to be no bigger than 30 kWh/d per person—but this competes directly with land needed for food production.

Waste Incineration

If the UK adopts the high incineration rates of countries like Denmark, Sweden, and Switzerland, domestic and agricultural waste can contribute to electricity generation.

  • Plausible output: The total contribution of waste incineration is approximately 1.1 kWh/d per person.

5. The Wall of No: Social Constraints and the 18 kWh/d/p Estimate

When the total numerical potential of all plausible local UK renewable resources is aggregated, the technical capacity is substantial, perhaps around 50 kWh/d/p. This technical figure might be enough to cover the required future electrical demand of 48 kWh/d/p.

However, the laws of arithmetic must confront the reality of public sentiment: the British are excellent at saying “no.” Public opposition constitutes a massive social ceiling that severely restricts attainable output.

Specific objections include:

  • Wind farms are deemed “ugly noisy things”
  • Forestry (for biomass) “ruins the countryside”
  • Waste incineration raises worries about health risks and traffic
  • The necessary infrastructure, such as “ugly powerlines coming ashore” from offshore wind facilities, is strongly opposed

The sources conclude that if one factors in these likely objections (the NIMBY effect), the maximum sustainable power Britain might realistically attain from its own renewables drops precipitously to approximately 18 kWh/d per person.

Realistic renewable limit: 18 kWh/d/p after social constraints (NIMBY effect)

Comparing this realistic 18 kWh/d/p supply against the existing 125 kWh/d/p consumption (or even the future electrical requirement of 48 kWh/d/p) leads to the foundational conclusion: “Realistically, I don’t think Britain can live on its own renewables—at least not the way we currently live.”

To bridge this immense gap, the next phase of planning must look beyond Britain’s physical and social ceilings, exploring centralized, high-density power sources that are either non-indigenous or non-renewable.