Geothermal energy taps the Earth's internal heat for a variety of uses, including electric power production, and the heating and cooling of buildings. Plants are another source of energy derived from the land. The organic matter that makes up plants is known as biomass. Biomass can be used to produce electricity, transportation fuels, or chemicals.


Aerial photo of a large green field. A mountain rises in the background covered by white clouds in a blue sky. Irrigation ditches are dug in rows throughout the field.Hawai‘i has an abundance of options for energy from the land, including geothermal and biomass from crops such as the sugar cane featured here.

GEOTHERMAL ENERGY BASICS

Many technologies have been developed to take advantage of geothermal energy—heat from the Earth. This heat can be drawn from hot water or steam reservoirs in the Earth that are accessed by drilling as well as the shallow ground near the Earth's surface that maintains a relatively constant temperature of 50°–60°F.

The variety of geothermal resources allows them to be used on large and small scales. A utility can use the hot water and steam from reservoirs to drive generators and produce electricity for its customers. In other cases, the heat produced from geothermal energy can be used to generate electricity for buildings, agriculture, and industrial plants. Still other applications use the heat directly from the ground to heat and cool homes and other buildings, or to provide heat for agricultural and other commercial processes.

Learn more about these applications on the National Renewable Energy Laboratory (NREL) Web site:

  • Geothermal direct use—producing heat directly from hot water within the Earth
  • Geothermal electricity production—generating electricity from the Earth's heat
  • Geothermal heat pumps—using the shallow ground to heat and cool buildings.

 

   

Photo of very tall light green grass sloping downward on a hillside. In the background are trees and more grass. The sky is overcast with sun peeking through. The ocean is in the background.This geothermal plant on Hawai‘i's Big Island produces as much as 30 megawatts of power and has near-zero emissions. The facility went online in 1993 and delivers renewable energy to the Hawai‘i Electric Light Company.

GEOTHERMAL ENERGY IN HAWAI‘I

Serious hydrothermal exploration did not begin until the 1960s. Within a decade, the first productive geothermal well was drilled on Hawai‘i's Big Island and, by 1982, steam from that well was being used in a demonstration pilot plant to produce electricity for consumer use. Today, geothermal energy from a commercial power plant supplies 20% of Hawai‘i's Big Island's energy needs and an expansion of the 30-MW Puna Geothermal Venture power plant is expected.  All fluids brought to the surface are injected deep into the ground after being used to generate electricity, ensuring that the plant has essentially zero emissions under normal operation. 

Commercial geothermal resources in Hawai‘i have only been demonstrated to exist in the Puna District of the Hawai‘i's Big Island, in Kilauea’s east rift zone.  However, it is likely that other hot spots exist which could also be used to generate geothermal electricity.

To date, Hawai‘i has no commercial geothermal direct use or heat pump applications.  However, geothermally-warmed water leaks from Hawai‘i's Big Island's aquifer into the ocean at a number of locations, providing warm ponds used extensively for recreation.

 

Photo of very tall light green grass sloping downward on a hillside. In the background are trees and more grass. The sky is overcast with sun peeking through. The ocean is in the background.Biomass energy from garbage, landfill gas, sugar cane, agricultural waste, and vegetable oil can provide Hawai‘i with numerous energy benefits.

BIOMASS ENERGY BASICS

Humans have used biomass energy or "bioenergy"—the energy from plants and plant-derived materials—since we began burning wood to cook food and keep warm. Although wood is still the largest biomass energy resource today, others include food crops, grassy and woody plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes. Even the fumes from landfills (which are methane, a natural gas) can be used as a biomass energy source.

On the NREL Web site, learn about he uses of biomass energy, including:

  • Fuels—converting biomass into liquid fuels for transportation
  • Power production—burning biomass directly, or converting it into gaseous or liquid fuels that burn more efficiently to generate electricity
  • Bioproducts—converting biomass into chemicals for making plastics and other products that typically are made from petroleum.

NREL is working to develop biorefineries that will convert biomass into a range of valuable fuels, chemicals, materials, and products—much like oil refineries and petrochemical plants do. Learn more on the NREL Web site.

 

 

BIOMASS ENERGY IN HAWAI‘I

With a wide range of growing conditions, soil types, weeds, and pests—and more than a century of experience in using biomass for power and fuel production—Hawai‘i's world-class engineers, agronomists, pathologists, foresters, entomologists, microbiologists, environmental specialists, chemists, economists, researchers, and others have developed an extensive base of knowledge and experience in both high-tech and low-tech approaches to cultivation, pest control, propagation, and thermal and chemical processing and conversion of a wide variety of plant species for biomass energy applications.

Biomass energy can provide an array of benefits for Hawai‘i. For example:

  • The use of biomass can reduce dependence on foreign oil because biofuels are the only renewable liquid transportation fuels available.
  • The use of biomass energy has the potential to greatly reduce greenhouse gas emissions. Burning biomass releases about the same amount of carbon dioxide as burning fossil fuels. However, fossil fuels release carbon dioxide captured by photosynthesis millions of years ago—an essentially "new" greenhouse gas. Biomass, on the other hand, releases carbon dioxide that is largely balanced by the carbon dioxide captured in its own growth (depending how much energy was used to grow, harvest, and process the fuel).
  • Biomass energy has the potential to boost Hawai‘i's agricultural industry. Studies are under way to determine the viability of using agricultural residues, including sugarcane bagasse and trash, macadamia nut shells, and pineapple processing waste, to produce electricity. Also under consideration are the growth and use of dedicated energy crops, such as hemp and banagrass, that can grow sustainably on land that can no longer support intensive food crops.

Examples of biomass energy use in Hawai‘i include:

  • Electricity from refuse-derived fuel: H-POWER (Honolulu Project of Waste Energy Recovery), the city and county of Honolulu's "garbage to energy" plant, is burning refuse-derived fuel to provide electricity, which it sells to Hawaiian Electric Company. Materials that do not burn, such as glass and metal, are removed and may be recycled. The plant produces approximately 8% of O‘ahu's electricity and, since it began operations in May 1990, has processed about 600,000 tons of waste per year, generating electricity that would otherwise have required about 600,000 barrels of oil annually.
  • Electricity from landfill gas: During the 1990s, methane collected from the Kapa‘a landfill on O‘ahu was burned to produce electricity. Heat from the turbine exhaust was used to dry gravel.
  • Biomass from sugarcane: Sugar factories in Hawai‘i burn bagasse to provide steam for sugar processing and electricity generation. Electricity that isn't needed for factory operations is sold to local utility companies. Ethanol made from sugarcane molasses has been produced in Hawai‘i and mixed with gasoline to produce fuel for automobiles. The sugar plantations on Kaua‘i and Maui have a capacity to produce a combined total of about 46 megawatts of power from biomass. Most of this is used internally by the factories for sugar processing.
  • Biomass from agricultural waste: Although the sugar plantations on the islands of O‘ahu and Hawai‘i are no longer in operation, "diversified agriculture" crops—coffee, macadamia nuts, watermelons, trees, flowers, and many others—are being grown at these locations. Waste products from these operations (and possibly even "energy crops") are used to produce electricity.
  • Biodiesel from vegetable oil: Used cooking oil is converted into biodiesel at facilities on Maui and O‘ahu. The biodiesel production facility on Maui can produce 150,000 gallons per year (2004); the O‘ahu plant's output is 400,000 gallons per year. Biodiesel may be blended with regular diesel and used in existing diesel engines in trucks, buses, boats, and stationary distributed generator systems.

 

 

  

Hawaii Clean Energy Initiative