How is energy produced?

ENERGY 101

Energy sources are often categorized as renewable or not, but perhaps a more accurate classification focuses on the type of reaction that converts energy into useful matter. Photo by simpson33/Getty Images

Many think of the Energy Industry as a dichotomy–old vs. new, renewable vs. nonrenewable, good vs. bad. But like most things, energy comes from an array of sources, and each kind has its own unique benefits and challenges. Understanding the multi-faceted identity of currently available energy sources creates an environment in which new ideas for cleaner and more sustainable energy sourcing can proliferate.

At a high level, energy can be broadly categorized by the process of extracting and converting it into a useful form.

Energy Produced from Chemical Reaction

Energy derived from coal, crude oil, natural gas, and biomass is primarily produced as a result of bonds breaking during a chemical reaction. When heated, burned, or fermented, organic matter releases energy, which is converted into mechanical or electrical energy.

These sources can be stored, distributed, and shared relatively easily and do not have to be converted immediately for power consumption. However, the resulting chemical reaction produces environmentally harmful waste products.

Though the processes to extract these organic sources of energy have been refined for many years to achieve reliable and cheap energy, they can be risky and are perceived as invasive to mother nature.

According to the 2022 bp Statistical Review of World Energy, approximately 50% of the world’s energy consumption comes from petroleum and natural gas; another 25% from coal. Though there was a small decline in demand for oil from 2019 to 2021, the overall demand for fossil fuels remained unchanged during the same time frame, mostly due to the increase in natural gas and coal consumption.

Energy Produced from Mechanical Reaction

Energy captured from the earth’s heat or the movement of wind and water results from the mechanical processes enabled by the turning of turbines in source-rich environments. These turbines spin to produce electricity inside a generator.

Solar energy does not require the use of a generator but produces electricity due to the release of electrons from the semiconducting materials found on a solar panel. The electricity produced by geothermal, wind, solar, and hydropower is then converted from direct current to alternating current electricity.

Electricity is most useful for immediate consumption, as storage requires the use of batteries–a process that turns electrical energy into chemical energy that can then be accessed in much the same way that coal, crude oil, natural gas, and biomass produce energy.

Energy Produced from a Combination of Reactions

Hydrogen energy comes from a unique blend of both electrical and chemical energy processes. Despite hydrogen being the most abundant element on earth, it is rarely found on its own, requiring a two-step process to extract and convert energy into a usable form. Hydrogen is primarily produced as a by-product of fossil fuels, with its own set of emissions challenges related to separating the hydrogen from the hydrocarbons.

Many use electrolysis to separate hydrogen from other elements before performing a chemical reaction to create electrical energy inside of a contained fuel cell. The electrolysis process is certainly a more environmentally-friendly solution, but there are still great risks with hydrogen energy–it is highly flammable, and its general energy output is less than that of other electricity-generating methods.

Energy Produced from Nuclear Reaction

Finally, energy originating from the splitting of an atom’s nucleus, mostly through nuclear fission, is yet another way to produce energy. A large volume of heat is released when an atom is bombarded by neutrons in a nuclear power plant, which is then converted to electrical energy.

This process also produces a particularly sensitive by-product known as radiation, and with it, radioactive waste. The proper handling of radiation and radioactive waste is of utmost concern, as its effects can be incredibly damaging to the environment surrounding a nuclear power plant.

Nuclear fission produces minimal carbon, so nuclear energy is oft considered environmentally safe–as long as strict protocols are followed to ensure proper storage and disposal of radiation and radioactive waste.

Nuclear to Mechanical to Chemical?

Interestingly enough, the Earth’s heat comes from the decay of radioactive materials in the Earth’s core, loosely linking nuclear power production back to geothermal energy production.

It’s also clear the conversion of energy into electricity is the cleanest option for the environment, yet adequate infrastructure remains limited in supply and accessibility. If not consumed immediately as electricity, energy is thus converted into a chemical form for the convenience of storage and distribution it provides.

Perhaps the expertise and talent of Houstonians serving the flourishing academic and industrial sectors of energy development will soon resolve many of our current energy challenges by exploring further the circular dynamic of the energy environment. Be sure to check out our Events Page to find the networking event that best serves your interest in the Energy Transition.


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Lindsey Ferrell is a contributing writer to EnergyCapitalHTX and founder of Guerrella & Co.

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40+ climatetech startups join Greentown, including a dozen from Houston

green team

More than 40 climatetech startups joined the Greentown Labs Houston community in the second half of 2025. Twelve hail from the Bayou City.

The companies are among a group of nearly 70 that joined the climatetech incubator, which is co-located in Houston and Boston, in Q3 and Q4.

The new companies that have joined the Houston incubator specialize in a variety of clean energy applications, from green hydrogen-producing water-splitting cycles to drones that service wind turbines.

The local startups that joined Greentown Houston include:

  • Houston-based Wise Energie, which delivers turnkey microgrids that blend vertical-axis wind, solar PV, and battery storage into a single, silent system.
  • The Woodlands-based Resollant, which is developing compact, zero-emissions hydrogen and carbon reactors to provide low-cost, scalable clean hydrogen and high-purity carbon for the energy and manufacturing sectors.
  • Houston-based ClarityCastle, which designs and manufactures modular, soundproof work pods that replace traditional drywall construction with reusable, low-waste alternatives made from recycled materials.
  • Houston-based WattSto Energy, which manufactures vanadium redox flow batteries to deliver long-duration storage for both grid-scale projects and off-grid microgrids.
  • Houston-based AMPeers, which delivers advanced, high-temperature superconductors in the U.S. at a fraction of traditional costs.
  • Houston-based Biosimo, which is developing bio-based platform chemicals, pioneering sustainable chemistry for a healthier planet and economy.
  • Houston-based Ententia, which offers purpose-built, generative AI for industry.
  • Houston-based GeoKiln Energy Innovation, which is developing a new way to produce clean hydrogen by accelerating natural geologic reactions in iron-rich rock formations using precision electrical heating.
  • Houston-based Timbergrove, which builds AI and IoT solutions that connect and optimize assets—boosting visibility, safety, and efficiency.
  • Houston-based dataVediK, which combines energy-domain expertise with advanced machine learning and intelligent automation to empower organizations to achieve operational excellence and accelerate their sustainability goals.
  • Houston-based Resonant Thermal Systems, which uses a resonant energy-transfer (RET) system to extract critical minerals from industrial and natural brines without using membranes or grid electricity.
  • Houston-based Torres Orbital Mining (TOM),which develops autonomous excavation systems for extreme environments on Earth and the moon, enabling safe, data-driven resource recovery and laying the groundwork for sustainable off-world industry.

Other startups from around the world joined the Houston incubator in the same time period, including:

More than 100 startups joined Greentown this year, according to an end-of-year reflection shared by Greentown CEO Georgina Campbell Flatter.

Flatter joined Greentown in the top leadership role in February 2025. She succeeded former CEO and president Kevin Knobloch, who stepped down in July 2024.

"I moved back to the United States in March 2025 after six years overseas—2,000 miles, three children, and one very patient husband later. Over these months, I’ve had the chance to hear from the entrepreneurs, industry leaders, investors, and partners who make this community thrive. What I’ve experienced has left me brimming with urgent optimism for the future we’re building together," she said in the release.

According to Flatter, Greentown alumni raised more than $2 billion this year and created more than 3,000 jobs.

"Greentown startups and ecosystem leaders—from Boston, Houston, and beyond—are showing that we can move further and faster together. That we don’t have to choose between more energy or lower emissions, or between increasing sustainability and boosting profit. I call this the power of 'and,'" Flatter added. "We’re working for energy and climate, innovation and scale, legacy industry and startups, prosperity for people and planet. The 'and' is where possibility expands."

NRG makes latest partnership to grow virtual power plant

VPP partners

Houston-based NRG Energy recently announced a new long-term partnership with San Francisco-based Sunrun that aims to meet Texas’ surging energy demands and accelerate the adoption of home battery storage in Texas. The partnership also aligns with NRG’s goal of developing a 1-gigawatt virtual power plant by connecting thousands of decentralized energy sources by 2035.

Through the partnership, the companies will offer Texas residents home energy solutions that pair Sunrun’s solar-plus-storage systems with optimized rate plans and smart battery programming through Reliant, NRG’s retail electricity provider. As new customers enroll, their stored energy can be aggregated and dispatched to the ERCOT grid, according to a news release.

Additionally, Sunrun and NRG will work to create customer plans that aggregate and dispatch distributed power and provide electricity to Texas’ grid during peak periods.

“Texas is growing fast, and our electricity supply must keep pace,” Brad Bentley, executive vice president and president of NRG Consumer, said in the release. “By teaming up with Sunrun, we’re unlocking a new source of dispatchable, flexible energy while giving customers the opportunity to unlock value from their homes and contribute to a more resilient grid

Participating Reliant customers will be paid for sharing their stored solar energy through the partnership. Sunrun will be compensated for aggregating the stored capacity.

“This partnership demonstrates the scale and strength of Sunrun’s storage and solar distributed power plant assets,” Sunrun CEO Mary Powell added in the release. “We are delivering critical energy infrastructure that gives Texas families affordable, resilient power and builds a reliable, flexible power plant for the grid.”

In December, Reliant also teamed up with San Francisco tech company GoodLeap to bolster residential battery participation and accelerate the growth of NRG’s virtual power plant network in Texas.

In 2024, NRG partnered with California-based Renew Home to distribute hundreds of thousands of VPP-enabled smart thermostats by 2035 to help households manage and lower their energy costs. At the time, the company reported that its 1-gigawatt VPP would be able to provide energy to 200,000 homes during peak demand.