Is It Possible To Have 100% Solar Energy?

Achieving 100% of our energy from solar power has long been a dream of many environmentalists and technologists. In theory, solar energy has the potential to fully displace fossil fuels and eliminate greenhouse gas emissions from the electricity sector. With solar photovoltaic and concentrating solar thermal technologies improving dramatically in efficiency and falling rapidly in cost over the past decade, the prospects for solar domination of global energy supplies is looking increasingly viable.

However, while the potential of solar power is enormous, actually achieving 100% solar energy faces substantial practical challenges. Solar energy remains an intermittent resource, available only when the sun is shining. Storing solar energy and ensuring round-the-clock reliability would require massive investments in energy storage and transmission infrastructure. Solar may be able to generate most of our electricity by mid-century, but fully displacing fossil fuels for all energy uses will require major systemic changes.

This article will examine the feasibility and requirements for achieving 100% solar power. While theoretically possible in the long run, the roadmap for getting there is filled with complex technological, economic and political hurdles. Realistically achieving a 100% solar-powered future would demand an unprecedented commitment of resources and coordinated effort.

Current Status of Solar Energy

Solar energy currently accounts for about 3% of total global electricity generation. However, solar power has been growing rapidly over the past decade, with an average annual growth rate of over 40%. In 2021, global solar PV installations reached a record 182 GW, bringing total worldwide capacity to over 1,000 GW.

Some countries now get a substantial portion of their electricity from solar. For example, in 2021 solar provided 15.5% of electricity generation in Australia, 14.2% in Spain, 13.6% in Greece, and 12.9% in Honduras, according to the International Energy Agency (1). Other leading countries for solar electricity include Italy (12.7%), Germany (12.2%), Chile (11.7%), Japan (10.5%), and the United States (4.3%). While solar currently meets a relatively small portion of global electricity demand, many experts predict continued rapid growth in the coming years.

Growth Potential for Solar

The cost of solar energy has declined rapidly in the past decade, making it increasingly competitive with fossil fuels. According to the National Renewable Energy Laboratory, the median installed price of solar PV systems fell by 68% between 2010 and 2020 across the residential, commercial, and utility-scale sectors [1]. This dramatic cost reduction is enabling accelerated growth in solar installations.

Several factors are driving down the cost of solar. Improvements in manufacturing techniques and economies of scale are lowering the cost of solar panels. New financing and leasing models are reducing upfront costs for consumers. Installation costs are decreasing as the solar workforce expands and processes become more efficient. Advances in solar panel technology are also increasing efficiency, allowing more electricity to be generated from the same sized systems [2].

With solar already at cost parity with fossil fuels in many markets, further cost reductions and efficiency gains will enable solar to continue its rapid growth worldwide. The potential for expansion is massive, as solar currently provides only about 3% of total global electricity generation [3]. As costs fall further, solar energy production could scale up dramatically in the coming decades.

Challenges of Intermittency

One of the biggest challenges with relying entirely on solar energy is its intermittent nature, meaning solar power generation fluctuates based on weather conditions and the time of day [1]. Solar energy can only be captured when the sun is shining, with output drastically reduced on cloudy days or at night. Solar generation peaks near midday and drops off in the evening as the sun sets. This variability makes it difficult to perfectly match solar supply with electricity demand, which also fluctuates during the day.

Intermittency creates imbalances in the electrical grid if supply and demand are not properly balanced. Having excess solar energy at midday but insufficient supply in the evening can lead to wasted energy without adequate storage. Relying completely on solar power would require advances in energy storage to capture excess daytime solar and large flexible capacity on the grid to ramp up when solar drops off each evening [2].

Energy Storage Solutions

Energy storage is critical for enabling high levels of solar and other renewable energy on the grid. There are several main options for utility-scale energy storage:

Batteries have become the dominant form of grid storage due to rapid cost declines over the past decade. Lithium-ion batteries in particular can provide 4+ hours of energy capacity and have <90% roundtrip efficiency. Major battery storage projects are being deployed worldwide, including the 400 MWh Moss Landing project in California (IEA).

Pumped hydro storage involves pumping water uphill into a reservoir when electricity supply exceeds demand and then releasing it through hydro turbines when needed. This is a mature technology that accounts for over 90% of global grid storage, but site options are geographically limited (Yale).

Compressed air energy storage compresses air in underground caverns or pipes during low demand. The pressurized air is then released to turn turbines when electricity is needed. There are only two large scale projects worldwide, but new innovations may improve efficiency and lower costs.

Transmission Infrastructure

As more renewable energy like wind and solar comes online, upgrades to transmission infrastructure are needed to handle the influx of distributed generation. Currently, there is a backlog of transmission projects waiting to be built due to permitting and siting challenges (Queued Up… But in Need of Transmission). Expanding and modernizing transmission helps integrate renewable energy sources across broader geographic regions (Increasing the Capacity of Existing Power Lines). However, the pace of new transmission development has been lagging, severely limiting potential greenhouse gas reductions from renewable energy (Transmission development pace ‘severely’ limits emissions reductions). To enable higher penetrations of renewables, regulators and utilities need to streamline siting and permitting processes to upgrade aging infrastructure as well as build new high-voltage transmission lines.

Advances in Forecasting

Advances in forecasting have allowed grid operators to better predict renewable generation and match supply with demand. According to a 2021 study, machine learning techniques can increase the accuracy of solar and wind forecasts by 15-25% compared to existing models. More accurate forecasts allow grid operators to schedule the right amount of dispatchable generation ahead of time.

The National Renewable Energy Laboratory (NREL) is at the forefront of solar and wind forecasting research. Their work focuses on developing high-fidelity forecasts that can be integrated into energy management systems to balance supply and demand in real time (NREL, 2022). Increased forecasting accuracy down to 5-minute intervals will be key to managing high renewable penetration.

Increased System Flexibility

One potential solution to handle intermittent renewable generation is to increase system flexibility. As defined by the National Renewable Energy Lab, system flexibility refers to “the ability of a power system to respond to changes in supply and demand” (Grid Flexibility). There are several ways to increase flexibility:

Flexible Generation: Traditional baseload generators like coal and nuclear plants are inflexible, operating continuously at maximum output. In contrast, natural gas plants can ramp output up and down quickly. Investing in flexible natural gas generation alongside renewables can provide crucial system support.

Demand Response: With demand response, end users voluntarily reduce energy use during peak times in response to price signals or incentive payments. For example, a utility might provide rebates for customers to allow remote adjustment of smart thermostats when needed. Demand response allows matching of load to intermittent renewable generation (NREL).

Grid Operating Reforms: Updating grid operating practices and market structures can also increase flexibility. This includes faster dispatch of energy resources, improved renewable forecasting, and market reforms that incentivize flexible generation. With the right policies, system operators can leverage flexibility to integrate higher shares of renewables.

Other Renewables

While solar energy has great potential, relying solely on solar to reach 100% renewable energy would be challenging due to its intermittency. Other renewable sources like wind, geothermal, and hydro can play an important complementary role in enabling high renewable grids (Jurasz 2020).

Wind power is an especially useful complement to solar, as wind speeds tend to be higher at night when solar generation is absent. Studies have shown that combining wind and solar can reduce curtailment, increase capacity factors, and lower costs compared to either source alone (Murphy 2023).

Geothermal provides consistent baseload power and can help balance the variability of solar and wind. Hydroelectric power can rapidly adjust output to offset changes in renewable generation. Using a diverse mix of complementary renewables can lead to a more reliable and resilient zero-carbon grid.

Conclusion

Though reaching 100% solar energy poses challenges, it may be feasible through continued innovation, investment, and integration of solar with storage, transmission, forecasting, system flexibility, and other renewables. Solar’s costs have declined dramatically, and capacity continues growing rapidly. However, intermittency remains an obstacle. Advances in energy storage, long-distance transmission, and forecasting can help address variability. System flexibility from grid modernization, demand response, and integration with other renewable sources also helps enable higher solar penetration. With coordinated efforts across technologies, market design, and infrastructure, a 100% solar future may be possible in some regions. But it will require overcoming daunting economic and technical hurdles. With diligent commitment to research, development, and systems-level thinking, 100% solar could shift from aspiration to reality.