THE SUPPLY OF ENERGY

In its World Energy Outlook 2022, the International Energy Agency projects that under the Stated Policies Scenario the world primary energy consumption will  increase by 19 percent from 2021 to 2050. How will the energy supply mix change to meet the higher demand? This question is addressed with the help of table V-1, which shows the projected supply by major energy source and the relative shares in 2021 and 2050. Starting with the shares, we notice that in 2021 the world energy supply was dominated by fossil fuels which accounted for nearly 80 percent of the total. Renewable energy sources contributed 12 percent, and the combination of nuclear power and traditional biomass added 8 percent. Within the fossil fuel category, all three major energy sources �" oil, natural gas, and coal �" accounted for similar shares. The big change from 2021 to 2050 is the large increase in the share of renewables, which increases by a factor of nearly 2.5, and the corresponding decline in the share of fossil fuels. The share of nuclear power and traditional biomass combined remains unchanged as an increase in the former is offset by a decline in the latter. The decline in the share of fossil fuels is determined primarily by the fall in the share of coal, which drops by 43 percent (11npercentage points). The combined share of oil and natural gas declines by only 11 percent (6 percentage points).

Within the context of sustainability, the absolute values are more telling. Although the share of oil and natural gas is projected to decline from 2021 to 2050, their total supply will actually be higher by 14 and 4 EJs respectively. Among fossil fuels, only the supply of coal is projected to decline.  More than eighty percent of the increase in the supply of renewable energy serves to satisfy the increase in consumption. Table V-1 makes it clear that the status quo of the energy expansion stage will persist at least until 2050. Unless the growth of energy consumption is substantially curtailed, the expansion of renewable energy will largely serve to meet increasing demand, and oil and natural gas will continue to play a significant role in the energy supply mix until the end of the century.

 

Table V-1. The Supply of Energy: 2021 and 2050^a

Energy Source                               Energy Supply^b                             Change in

         2021                        2050                    EJ           Share

   EJ          Share^c          EJ        Share^c

Renewable                       74         11.90            215      29.13           141          17.23

Biomass^d                            24           3.86              18       2.44             - 6          - 1.42

Nuclear                            30           4.82              46       6.23              16            1.41

Natural Gas                    146         23.47           150      20.33               4          - 3.14

Oil^b                                 183         29.42           197      26.69             14          - 2.73

Coal                                165         26.53           112      15.18            - 53       - 11.35

Total                                624      100.00           740     100.00           116

Fossil Fuels                     494        79.42            459      62.20            - 35       - 17.21

^aStated Policies scenario; ^bIncludes non-energy use; ^cSince the total is 2 TJ less than the sum, the shares are calculated with respect to the sum; ^dTraditional use.

Source: IEA (2022), World Energy Outlook 2022, Table A1, p. 435.

                    

What is potential supply of energy over the long-run for each of the above major energy sources? In addressing this question, I make a distinction between non-renewable and renewable resources and between reserves and resources. Non-renewable resources are finite stocks of fuels or minerals that exist naturally and are found under the surface of the earth. As components of the energy mix, they include coal, crude oil and liquid petroleum gases, natural gas, and uranium. Renewable resources are naturally-occurring flows of power �" such as wind, solar, and water (hydro or tidal) �" above the earth’s surface which can be transformed into mechanical energy (windmills, waterwheels) of electricity. Geothermal is structurally akin to non-renewable resources as it originates underground and is produced by some form of combustion, but is treated as renewable energy because its power source is practically inexhaustible heat arising from the earth’s core.     

Non-renewable Resources. Because these resources are in the form of natural materials, their quantity can be estimated or inferred. The amount of a natural resource that is known or hypothesized to exist is called occurrence. The occurrence of natural resource, say coal, comprises an identified and an undiscovered component. The former refers to deposits whose existence is known and their dimensions can be measured with high degrees of accuracy with the use of geological and engineering analysis. The latter refers to deposits that have not been discovered yet, but their existence and potential may be inferred from the characteristics of known resources. Reserves are a subset of discovered deposits, specifically the proportion that can be recovered profitably at any given time with the existing technology. The factors that determine the relationship between known deposits and reserves are identified in table V-2 which refers to the case of coal.

 

Table V-2. Factors Affecting the Relationship between Known Deposits and Reserves

1.    Original Resources

Minus: Already Extracted or Wasted during Previous Mining

     2. Remaining Resources

Minus: unavailable due to geological, environments, social, and technical constraints

     3.Available Resources

        Minus: Non-economic resources (extraction costs exceeds selling price

    4. Reserves

Source: USGS, “Assessing Coal Resources and Reserves”.

 

Table V-2 suggests two general conclusions. First, at any particular time, reserves are a small proportion of remaining resources. Second, both the discovery of resources and the ratio of reserves to resources are crucially dependent on technology, economic conditions, and environmental and social factors.

Fossil Fuels. The relationship between cumulative production (from 2021 to 2050), reserves, and resources is shown in table V-3. The first row shows the ratio of the cumulative supply of fossil fuels (from 2021 to 2050) to the level of proven reserves in 2021. For oil and natural gas, the amount projected to be produced over the next 29 years would exhaust 55 percent of proven reserves. If there were no changes in reserves during that period, they could support a similar cumulative consumption for about 24 additional years. However, reserves tend to increase with demand. For example, during the two decades from 2000 to 2020, new reserves of oil and natural gas not only accommodated consumption but rose by one-third and 36 percent, respectively. The reason for the expansion of reserves over time is the existing low rate of resource depletion. As shown in the second row, proven reserves of oil and natural gas in 2021 represent less than 30 percent of resources. Of course, accessing additional resources with current technology would require additional costs, but technology itself does not remain static. How the interaction of potentially higher extraction costs with advancing technology will affect future trends in the price of oil and natural gas is not known, but depends also on the pace of demand. A declining demand would mitigate the need to find additional reserves and would provide more time for cost-saving technological changes.        

Coal is even more abundant than oil and natural gas. The cumulative supply from 2021 to 2050 represented only 13 percent of reserves, and reserves amount to 5 percent of resources. The abundance of fossil fuels was recognized by the IEA,  “all fuels are at a level comfortably sufficient to meet the projection of global energy demand to 2050 in all scenarios.”¹

 

Table V-3. Consumption, Reserves, and Resources of Fossil Fuels: 2021 to 2050

                                     Natural Gas        Oil            Coal

Ratio of Cumulative Consumption

  to Proven Reserves (%)                                    54.9                  54.5           13.3

 

Ratio of Proven Reserves to

  Resources (%)             27.2                  28.3              5.2

Source: Author’s calculations based on IEA (2022), Table A1, p. 435 and Table B3, p. 467.                          

 

While abundant, fossil fuel resources are not spread evenly throughout the globe. As shown in table V-4, coal reserves are geographically concentrated. In 2021, forty-three percent of reserves were located in the Asia-Pacific region and an additional 24 percent in North-America, for a combined share of 67 percent. Fairly large concentrations are also found in Europe and Eurasia with a combined share of 30 percent. A similar concentration exists in coal consumption as the Asia-Pacific region accounts for 79 percent of the total. Natural gas reserves are as concentrated as coal’s, with Eurasia (32%) and the Middle East (37%) leading all regions with a combined share of 69 percent. Resources are less concentrated as four of the seven regions have shares between 14 and 21 percent. The largest consumer of natural gas is North-America with a share of 26 percent, followed by the Asia-Pacific region with 22 percent, for a combined share of nearly fifty percent. Three of the other five regions have consumption shares in the narrow range of 13 to 16 percent. A large concentration of reserves is also found in the case of oil, with the Middle East containing more than half of the total. An additional 30 percent is found in the Americas. Resources are less concentrated. North-America has the largest share (39%) and three regions have shares within the narrow range of 13 to 18 percent. The largest user if oil is the Asia-Pacific region (38%), followed by North-America (24%). These two regions combined account for nearly two-thirds of world oil consumption. Europe is a distant third with 14 percent.       

 

Table V-4. Consumption, Reserves and Resources by Region in 2021

Region                 Pop.            Coal: Share of                                     NG: Share of                      Oil: Share of

       Use      Reserves    Res’ces       Use      Reserves    Res’ces       Use   Reserves   Res’ces

 

North America       6.4            6.9      23.9            40.3         26.2        7.3            18.4          24.3       13.5         39.2                 

C./S. America        6.7            0.8        1.3              0.3           3.8        3.6            10.4            6.0       16.6         13.8

Europe                   8.9            6.5      12.7              4.7         14.8        2.3              5.7           14.1        0.9           1.8

Eurasia                  3.0             3.9      17.8              9.7        15.7       31.5            20.9            4.7        8.3          15.2  

Middle East           3.2             0.1       0.1              0.2         13.5      37.0            14.9            8.8       50.7         18.1

Africa                  17.5             2.7       1.4              1.6          4.1         8.7            12.6            4.3         7.1           7.2

Asia Pacific         54.2           79.0     42.8            43.1        21.8        9.6             17.1          37.8         2.8          4.5 

Source: IEA (2022), World Energy Outlook 2022, Author’s calculations based on table A.8, p451, table A.12, p. 453, table A.14, p. 454, table B.1, p. 464, table B.3, p. 467.

 

The oil sector has the unique feature of a cartel with the capacity to influence its price by controlling production. As shown in table V-5, in 2020 OPEC+ controlled eighty percent of proven oil reserves, and its oil production in 2021 accounted for 55 percent of the world’s total. Despite the expansion of renewable energy, according to IEA projections, the market of OPEC+ will not subside in the future, but its share of oil production will actually increase by 2.5 percentage points from 2021 to 2050.     

 

Table V-5. Oil Reserves and Production by OPEC Countries: Shares, Selected Years

                                   Shares

             Reserves                     Production

                2020                     2021          2050

 

OPEC       70.1                     35.3            38.8

OPEC +    79.7                     54.8            57.3

Source: IEA (2022), World Energy Outlook 2022, Table 7.3, p. 336; BP (2021), Statistical Review of Worl Energy 2021, p. 16; BP (2021), Statistical Review of Worl Energy 2022, p. 15.

      

Nuclear Power. Nuclear power is the energy released by nuclear reactions to generate electricity. Under current technology, the electricity is generated through nuclear fission which involves splitting the nucleus of an atom into smaller parts. The material used in the nuclear reaction is uranium. Therefore, when we are analyzing the material constraints to nuclear power, we are effectively dealing with the quantity of uranium resources. The available information on uranium mining leads to the following conclusions. First, in 2021 recoverable resources would be sufficient to meet production at the 2021 level for 127 years. The expansion of nuclear power would require the addition of new resources or it would shorten the length of the production capabilities. Second, the production of uranium is highly concentrated. In 2021, 45 percent of uranium was mined in Kazakhstan and the top five producers accounted for 84 percent of the total. Third, uranium reserves are less concentrated than production, but the top five producing countries still control 61 percent of the total, and the top ten producing countries account for over 80 percent of total resources. 

In the case of nuclear power, however, the factors constraining its utilization extend beyond the size of recoverable resources. As pointed out by the Nuclear Energy Agency, “The expansion of nuclear power is mainly policy-driven and faces challenges due to large upfront capital costs, complex project management requirements and often long permitting processes.”² To these may be added the perceived risk arising from the nuclear disasters at Three Miles Island (USA, 1979), Chernobyl (Ukraine, 1986), and Fukushima (Japan, 2011). For all these reasons, fission nuclear power is not expected to undergo a great expansion over the next thirty years and its share of primary energy consumption is projected by the IEA to increase moderately from 4.8 percent in 2021 to 6.2 percent in 2050.

 

Table V-6. Shares of Uranium Production and Recoverable Resources in 2021

Country      Share of

          Production       Resources

 

Kazakhstan                                  45.6                 13.0

Namibia  12.0                   8.0

Canada      9.8                 10.0

Australia   8.8                 28.0

Uzbekistan                                     7.4                   2.0

Sum         83.6                 61.0

Russia       5.5                   8.0

Niger         4.7                   5.0

China         3.4                   4.0

India          1.2                    n/a^a

South Africa                                   0.4                   5.0

Sum         15.2                 22.0 

Rest of the World                           1.2                 17.0

^aLess than 1 percent

Source: World Nuclear Association (2023), “World Uranium Mining Production,” unnumbered tables.

       

 Renewable Resources. There is a large variety of potential renewable resources. Since most of them are used in the generation electricity, it may be useful to review the role of electricity in the energy mix. The first panel of table V-7 shows the distribution of generating capacity by energy source for 2021 and 2050.  The IEA projects that generating capacity will increase at the average rate of 3.1 percent per year from 2021 to 2050. Generating capacity from renewable energy sources and from battery storage will grow faster than the average. As a result, their shares will rise by 29 and 6 percentage points, respectively. By 2050, three-quarters of generating capacity will be based on the combination of renewables (69%) and  battery storage (6 percent).  Nuclear capacity will grow at a below-average rate and its share will decline by 2 percentage points to 3 percent in 2050. Capacity based on fossil fuels will decline slightly and its share will fall by more than half to 21 percent in 2050. Basically, over the 2021-2050 period the addition to generating capacity from renewables (10,375 GW) will satisfy the additional demand (11,601GW). Because generation per unit of capacity is not equal for all energy sources, the distribution of electricity generated may differ from that of capacity. As shown in the second panel of table V-7, electricity generation is projected to grow at two-third the rate of capacity. Only in the case of nuclear power, the projected growth of generation exceeds the growth of capacity. The changes in shares of generation by energy source are similar to the changes in the shares of capacity.   

 

Table V-7. Percentage Distribution of Electricity Generation and Capacity by Energy Source, 2021 and 2050

                  Average Annual                Percent of Total^a

                  Percentage Change         2021             2050

Generating Capacity (GW)           

   Renewables        5.0                    40.1              69.0

   Nuclear                                                    1.2                      5.1               3.0

   Hydrogen + Ammonia                             n/a^b                      0                 0.1

   Fossil Fuels                                           - 0.2                     54.5             21.4

   Battery Storage                                      14.3                      0.3               6.5

   Total                    3.1

Generation (TWH)                                  

    Renewables        4.9                    28.5             65.2

    Nuclear               1.5                      9.8               8.6

    Hydrogen + Ammonia                             n/a^c                       0                 0.1

    Fossil Fuels      - 1.0                    61.7             26.1     

      Total                    2.0

^aWhen the sum is slightly different than the total, the shares are calculated with respect to the sum. ^b Increased from 0 in 2021 13 GW in 2050. ^c Increased from 0 to 44 TWH from 2021 to 2050.

Source: Author’s calculations based on (IEA, 2022, World Energy Outlook 2022, table A.1a, p. 435, and table A.3a, p. 438).

 

Despite the expansion of electricity generation, the shares of world energy consumption change only moderately from 2021 to 2050. Over a period of 29 years, the share of electricity expands by only 8 percentage points (about one percentage point every four years). The share of gaseous fuel remains virtually unchanged and that of liquid fuel declines by less than 3 percentage points. Only the share of solid fuel declines and by less than one would expect (about five percentage points). In terms of quantities, the consumption of both liquid and gaseous fuel actually increases at a rate slightly lower than that for the average consumption. Only the consumption of solid fuel declines and by only 7 percent over a 29-year period. What the IEA projects basically involves an increase in the consumption of energy from renewable resources that largely offsets the decline in the consumption of energy from solid fuels. If the share of renewable energy in total final consumption increased at the same pace as from 2021 to 2050 (11.2 percentage points over a 29-year period), it would take 80 additional years for renewables to become the dominant energy source (a share in excess of 50 percent). Even if renewable energy increased at a faster rate after 2050, it would take more than thirty additional years to become dominant. This means that for most of this century, if not beyond it, the world will remain in an energy proliferation stage.  

 

 

Table V-8. Distribution of World Final Energy Consumption by Energy Source: 2021 and 2050

 

                           Average Annual           Percent of Total

                           Percentage Change      2021         2050

 

Electricity               1.9                            19.8          27.8

Liquid Fuel             0.5                            38.7          36.0

Gaseous Fuel          0.7                            16.4          16.2

Solid Fuel             - 0.3                            21.4          16.0

Heat and Other        1.1                             3.7           4.0

Total                        0.7            

Source: Author’s Calculations based on IEA (2022), World Energy Outlook 2022, Table A.2a, p. 436.

 

I now discuss the potential of the main sources of renewable energy. As a background, I present in table V-9 the distribution of renewable energy by source in 2021 and 2050. We can identify four main categories of renewable resources depending on the ultimate source of energy: water, sun light, wind, and biological material. 

Starting with the first panel, we notice that in 2021 hydro dominated renewable electric generation with a 41 percent share. Solar (27%) and wind power (25%) added over 50 percent for a total of the three main renewable sources of 94 percent. The dominance of these three renewable energy sources is projected to continue in 2050 with a share of 96 percent. The only difference in 2050 is the reversal of the roles of solar and hydro with the share of the former rising to 55 percent and that the latter falling to 15 percent.  A similar pattern is found for electricity generation. In 2021, hydro is the top source with a share of 54 percent, and the combination of hydro, solar and wind accounts for 90 percent of the total. In 2050, the share of the top three renewable energy sources edges up by 2 percentage points, and a decline of 33 percentage points in the share of hydro is offset by an increase in the shares of solar (up 26 points) and wind (up 10 points).   

 

TableV-9. Distribution of Renewable Energy by Source, 2021 and 2050.

                    Average Annual               Percent of Total

                    Percentage Change          2021         2050

Generating Capacity 

   Water Power

   Hydro               1.4                            41.4          14.8

   Marine            13.3                               0             0.3

   Geothermal      5.0                              0.5            0.5

   Sum                  1.5                            41.9          15.6

   Solar                 7.6                            27.4          55.3

   Wind                 5.1                            25.4          26.1

   Bioenergy         3.0                              5.3            3.0

   Total                  5.0                          100.0       100.0

Generation

   Water Power 

   Hydro               1.6                            53.7          21.0

   Marine            17.0                               0             0.3

   Geothermal       5.6                             1.2            1.4

   Sum                   1.8                           54.9          22.7  

   Solar                  9.0                           12.6          38.4

   Wind                  6.2                           23.2          32.9

   Bioenergy          3.4                             9.3            6.0

   Total                  4.9                          100.0        100.0  

Source: Author’s calculation based on IEA (2022), World Energy Outlook 2022, Table A.3a, p. 438.             

 

Water Power: Hydro. Hydro-electricity is generated through the transformation of the kinetic energy of falling water in several steps: damming a water flow creates a water reservoir; an opening in the dam allows a controlled amount of water to flow through a pipe (penstock); the falling water spins a turbine; this movement forces the magnets inside a generator to rotate, generating electricity in the process.

Because there are necessarily a limited number of suitable water-flowing sites on earth, hydro-electricity is a renewable resource, but a finite one. When measuring the size of the hydro resource, it is useful to distinguish a number of concepts.  The gross potential measures the total electricity generation in the case where all available sites were developed. The technical potential measures the electricity generation from sources that could be developed using existing technology. The portion of the above that could be developed and sold at a competitive price is called economically feasible potential. According to Hoes at al. (2017), the gross potential of all water flowing locations in the world would amount to 104,000 TWh and the “generation potential” (assumed as half of gross potential) would be 52,000 TWh. This is nearly eight times the projected hydro-electricity generation in 2050 and slightly more than the projected total electricity generation for the same year.  According to a separate study, the global gross potential amounts to 128,000 TWh of electricity generation, but the technical and economically feasible are only 26, and 21,000 TWh, respectively. Still, the lower value is 3 times the projected hydro generation in 2050.³   

 

Hoes et al. (2017) also estimated that 68 percent of the generation potential involves large scale generation (at least 10 MW of capacity). This situation creates some impediments to site development. First, the larger is the site, the greater is the required up front capital expenditure and the longer the construction time. Second, the development of a larger site will lead to a more extensive area that end up under water, and to more extensive and varied ecological effects. This, in turn, will involve more complex and time-consuming permission processes.

 

Developed hydro sites can also serve other functions, especially storage of electricity generated from renewable energy sources with intermittent generation patterns. Currently this storage system accounts for over 90 percent of the total and its potential is quite large. A study by a research team at the Australian National University  has identified 530 thousand worldwide suitable for pump-hydro storage and have estimated a capacity of 22 thousand TWh of electricity.⁴ While recognizing that pump-hydro storage faces similar financial and regulatory barriers as standard hydro-electric generation, we must also recognize two important features. First, the combined capacity of hydro-generation and pumped-storage is quite large. Second, the impediments to its full development are not technical in nature.        

 

Water Power: Marine. There are four types of marine power: tidal, wave, ocean thermal, and salt gradient. I will briefly describe the potential of each.

 

Tidal energy results from the gravitational rotation of the earth and its relationship to sun and moon. It arises from the movement of ocean waters during the rise and fall of tides. It is technically related to standard hydro power as it directly activates turbines and generators. There are three forms of tidal power: tidal streams, barrages, and tidal lagoons. Tidal streams are naturally-occurring ocean currents whose power is harnessed by placing turbines under water. A barrage is a dam that traps ocean water at high tide and releases it at low tide through pipes that drive turbines, as in the case of standard hydro power. Tidal lagoons are similar to barrages as they also create temporary reservoirs at high tide. Unlike barrages, which tend to dam river estuaries, the tidal lagoons can be built along coastlines where rising ocean water can be trapped through natural or man-made barriers.

 

The potential of tidal power is significant. According to Boshell et al. (2020), tidal power has the capacity to generate 1.2 TWh per year. How much of this potential can be realized depends a variety of factors. In addition to the developmental obstacles shared with traditional hydro power (financial and environmental), the development of tidal power also faces technical constraints related to the construction and maintenance of moving machines subject to erosion from salt water. Because technology evolves over time, the future potential of tidal power may be larger than current estimates.

 

Wave energy is a type of renewable energy resulting from the motion of waves. It has the highest energy density of any renewable source. The devices that transform this kinetic energy into electricity may be fixed to the shoreline (shoreline devices), may be floating near the shore (shoreline devices), or may be fixed to the ocean floor (offshore device). The potential of wave energy is very large. According to the aforementioned study by Boshell et al. (2020), wave energy has the capacity to generate 29,500 TWh per year. This is equivalent to nearly 60 percent of the projected total electricity consumption in 2050.

 

Ocean thermal energy conversion (OTEC) is a process that produces energy by exploiting the temperature difference (heat gradient) between the warm water at the ocean’s surface and the cold water at the bottom. When this difference is large enough (at least 20 degrees centigrade) is can generate electricity by rotating a turbine. Because this renewable energy source depends on temperature differences, it is affected by changes in climatic conditions. According to a study by Du et al. (2022), the potential electricity that it can generated worldwide by OTEC is estimated to increase from about 20,000 TWh in 2010 to about 27,000 TWh in 2050 and approximately 30,000 TWh in 2070 due to the expansion of the area suitable for OTEC and rising power potential density.⁶ If we confine potential development to the more economical “exclusive economic zone (EEZ), the above estimates are cut in half. This means that in 2050, the estimated OTEC potential would be capable of generating roughly one-quarter of the projected world electricity consumption.                 

 

Salt gradient electricity generation is based on the differential in chemical pressure created by differences in salinity between saltwater and fresh water. Two main processes are used in this technology: reverse electrodialysis (RED) and pressure-retarded osmosis (PRO). Both processes use special semi-permeable membranes. The potential of this renewable energy source is substantial. According to Alvarez Silva et al. (2016), the theoretical potential amounts to 15 thousand TWh per year, but the realistic figure under current technology is only 625 TWh per year.⁷ According to a separate study, the realistic potential is about 5 thousand TWh per year.⁸

 

The greatest potential for marine generation of electricity is associated with wave energy. The combined potential of the other three sources is about 60 percent of the above. Together, these four sources of marine-based energy have the potential of supplying all the world electricity needs in 2050. The development of this potential faces many obstacles, some similar to hydro-electricity (capital costs and environment effects) and others of a technical nature. Even with these obstacles, the long-term potential is much higher than the installed capacity projected by the IEA for 2050. The important point is that this resource, being renewable, is not depleted over time and will be available whenever technological developments facilitate its development. 

 

Water Power: Geothermal. Unlike other sources of renewable energy, geothermal energy is derived from the heat within the Earth’s crust. It possesses the unique capacity of being available 24 hours a day and 365 days a year. Geothermal resources take the form of hot water reservoirs that exist naturally or are man-made. This resource is suitable for various applications, depending on the heat of the water in reservoir. High-temperature water or vapor is used for electricity generation. At intermediate-temperatures, geothermal power can be used directly for heating and cooling purposes. In this application, it has the advantage of flexibility as it can be scaled from small to large buildings. At low and steady temperatures, it can be combined with heat pumps for heating and cooling.

 

The geothermal power potential is quite large. Even confining the estimate to what may be harnessed with existing technology, the actual potential amounts to about 90 EJ of energy, equivalent to 16 percent of projected global final energy consumption in 2050⁹. Because this is a small portion of the theoretical potential resource (the heat within the Earth), this value is likely to increase over time in response to technological advancements.  

 

Solar Power. Solar power is derived by the conversion of sun light into heat or electricity. The surface of the earth is irradiated at the average rate of 343 Watts per square meter which yields a total for the globe of 1,715x10¹⁴ Watts. If we recognize that 30 percent of sun light is reflected before reaching Earth and confine the irradiated area to the land mass, the potential solar power is reduced to 360x10¹⁴ Watts. Finally, considering that not all land mass is suitable for harnessing solar power and assuming suitability for only half of the land surface, we end up with a potential solar power resource of 66x10²² Joules. This amount is several orders of magnitude higher that the total world energy consumption in 2021.¹⁰

   

There are three main technologies for harnessing solar power: Photovoltaic cells (PV), thermal solar power, and architecturally-aided solar power. Their potential is briefly discussed below.

 

Photovoltaic (PV) cells are the most common solar power device and they directly transform sun light into electricity. One of their advantages over other forms of renewable energy is their versatility as their use extends from powering a single lightbulb, to powering a single house, to form a large solar park with capacity reaching the GW level. One of the important applications of PV panels is rooftop installation to supply energy to a single house, an apartment building, or a commercial building.  The potential of rooftop PV electricity generation has been studied by researchers at the Imperial College in London. Mapping 130 million square meters of global surface land, they identified 0.2 million square kilometers of rooftop area and estimated that this area has the potential of generating 27 PWh of electricity per year, which represents more than four times the electricity used by households in 2019 and 18 percent more than the total electricity consumption in that year.¹¹ The potential of PV electricity generation in the remaining surface area may be even greater as it takes 4-5 acres of land for a 1 MW PV farm that generates close to 1.5 GWh of electricity per year¹²      

 

Thermal Solar Power. This technology is largely based on the use of mirrors for concentrating sun light onto a receiver. The solar energy so harnessed heats a fluid in the receiver, and this heat can be used directly in a variety of industrial processes or to generate electricity in a manner similar to power plants that use fossil fuels. This technology is best suited for large applications, and the best locations for it are deserts. Its potential may be even greater than PV.¹³ It should be stressed that the potential of PV and concentrating solar energy cannot be added because their devices would be competitors for suitable sites. It suffices to note, however, that their combination, adjusted for overlapping, has the potential to satisfy current and future global energy needs.

 

Architecturally-Aided Solar Power. This category of solar energy contains two types of application: incorporation of solar devices into buildings, and passive solar energy collection. In the former, rooftops and sides (cladding and windows) can be structured to incorporated solar energy devices. The potential of solar energy collected on rooftops has already been shown. The area of the sides is larger than that of roofs, but its solar energy potential is smaller for two reasons. First, a  large portion of the area has little or no exposure to sunlight. Second, incorporation of solar devices is more suitable for new buildings. In the case of passive solar energy, the building components �" windows, walls, and floors - become the passive devices that collect, reflect, store, and distribute solar energy. However, only south-facing sides are suitable for this architectural application and economics may confine these applications to new construction. For a new building, the potential of passive solar gain is not insignificant. According to D. Rucker Coleman (2023), a 2,000 square feet house in Seattle with south-side glazing equivalent to 5% of the floor area could gain from the sun 17 percent of its heat requirements. In a sunnier place like Denver, this percentage would increase to 30 percent.¹⁴             

 

Wind Power. Wind power is the kinetic energy of the wind harnessed by turbines. It can be used to generate electricity or to power mechanical devices. Turbines can be located onshore or offshore. Estimates of the potential of wind power vary depending on methodology and coverage. According to the Dutton Institute, wind power has the potential of generating more than 3,000 EY of energy, 82 percent of which is from onshore installations.¹⁵ Choi (2012) summarizes the results of two separate studies that show the large potential of wind power. In the first study, Katherine Marvel estimated 400 TW of generating capacity from surface winds and 1,800 TW from winds throughout the atmosphere. In the second study, Jacobson and Archer focused on large turbines operating at the conventional height of 330 feet and estimated a generating capacity of 250 TW over the entire surface of the earth, both land and sea.¹⁶ Lu, McElroy, and Kiviluona (2009) confined their calculations to non-forested, ice-free, non-urban areas. They estimated that a network of onshore 2.5 MW turbines operating at 20 percent of their rated capacity could generate five times the global energy consumption from all sources.¹⁷ Limiting its analysis to close-to-shore offshore sites globally, the IEA estimates a potential electricity generation of 36,000 TWh, almost enough to meet projected world electricity demand in 2040.¹⁸

Large as they may be, these estimates may underestimate the full potential of wind power because they refer only to electricity generation with large turbines. Great strides have been made recently in the development of small turbines that can even be installed on rooftops, adding to the solar energy that can be harnessed by the same site.           

Bioenergy. This is renewable energy derived from biomass (from forests or agricultural crops), waste, and other renewable sources. It can be used to generate electricity and heat or provide transportation fuels. Its potential depends largely on surplus agricultural land, but it is quite large. The IEA estimates its potential at 467 EJ per year, equivalent to nearly one-third of the global primary energy consumption projected for 2050.¹⁹ A much higher potential is suggested by Ludanai and Vinterbach (2009). After reviewing a variety of studies, they concluded that the potential of bioenergy in 2050 ranges between 1,135 and 1,300 EJ, which is at least 50 more than the projected global primary energy supply for that year.²⁰

Green Hydrogen. This form of energy is hydrogen produced through electrolysis using renewable resources. It can be used to store renewable energy, to generate electricity, in a variety of industrial processes, and in chemical production.  Because it is not a primary energy source, its potential cannot be added to that of other renewable energy resources. Still, it can be an important component of the final energy consumption mix and can help indirectly to enhance the versatility of intermittent primary renewable energy resources.

This brief survey of the energy mix leads to two main conclusions. First, there is enough potential energy from all sources to satisfy current or projected energy demand over the foreseeable future. Second, global energy can be satisfied by that portion of renewable energy potential that can be competitively developed under current technology. The fundamental issue with the energy supply is not scarcity, but the environmental and social cost of the current energy mix. Alternative policy approaches to this issue are discussed in the next chapter.   

Notes

¹International Energy Agency, “World Energy Outlook 2022”, p. 468. 

²Nuclear Energy Agency and International Atomic Energy Agency, 2023, Uranium 2022: Resources, Production Demand, OECD, p. 133.

³Zou, Y., M. Hesazy, S. Smith, J. Edmous, H. Li, L. Clarke, and A. Thomson, 2015, A Comprehensive View of Global Potential for Hydrogenerated Electricity, Energy and Environmental Science, Issue 9.      

⁴Australian National University, 1 April 2019, “ANU finds 530,000potential pumped-hydro sites worldwide”.

⁵Boshell, Francisco, Roland Roesch, Alessandra Salgado, and Judith Hecke, 3 June 2020, “Unlocking the potential of Ocean Energy: from megawatts to gigawatts,” Energypost.EU.

⁶Tianshi Du, Zhao Jing, Lixin Wu, Hong Wang, Zhaoui Chen, Xiaohui Ma, Bolan Gay, and Haiyuan Yang (2022), “Growth of Ocean Thermal Energy Conversion Resources under Greenhouse Warming Regulated by Oceanic Eddies,” Nauee Communications, 13, Artcicle No. 7249.

⁷O.A. Alvarez Silva, A.F. Osorio, and C. Winter, 2016, “Practical Global Salinity Gradient Energy Potential,” Renewables and Sustainable Energy Reviews, Vol. 60, pp. 1387-1395.

⁸ Andrew Tunnicliffe, 8 June 2021, “Making Blue from RED �" The Potential of Salinity Gradient Power,” Power Technology.

⁹Dutton Institute, “Geothermal Potential �" Earth 104”.

¹⁰Dutton Institute, “Energy Potential and Utilization,”

e-education.psu.edu/earth104/node/950.

¹¹Simon Levey, 8 October 2021, “Study Finds Huge Global Potential for Energy from Rooftop Solar Panels,” Imperial College, London.

¹²Tom Gill, 26 January 2023, “The 16 Largest Solar Farms in the World in 2023”.

¹³Franz Trieb, Christof Schillings, Merlene O’Sullivan, Thomas Pregger, and Carsten Hoyer Klick, 2009, “Global Potential of Concentrating Solar Power”.

¹⁴Debbie Rucker Coleman, 21 June 2023, “Why Homeowners Should Use Passive Design,” Solar Today.

¹⁵Dutton Institute, “The Potential of Wind Power �" Earth 104.

¹⁶Charles Q. Choi, 10 September 2012, “Studies Show Wind Power’s Massive Potential,” Inside Science.

¹⁷Lu, Xi, Michale B. McElroy, and Juha Kiviluona, 2009, “Global Potential for Wind-generated Electricity,” Proceedings of the National Academy of Sciences of the United States of America, 106(2): 10932-10938.

¹⁸IEA, “Wind,” www.iea.org/energy-systems/renewables/wind

¹⁹IEA, “Potential Contribution of Bioenergy to the World’s Future Energy Demand”.

²⁰Svetlana Ludanai and Johan Vinterbach, 2009, “Global Potential of Sustainable Biomass for Energy,” SLU, Report 2009:13.

Reference

Hoes, Aoc, Ljs Meiser, Rj van der Ent, Nc van der Giesen, 2017, “Systematic high-resolution assessment of global hydropower potential,” Plus One, 12(2): e0171844. https://doi.org/10.1371/journal.pont.0171844.