Solar energy is usually the first form of green energy that comes to mind when people think about renewables. It’s certainly the most commonly used system for residential, commercial, and now grid scale, non-fossil fuel energy production.
Solar cells are a special type of semi-conductor device that uses sunlight to produce electricity. They are manufactured and processed in a similar fashion as computer memory chips. Solar cells are primarily made up of silicon which absorbs the photons emitted by sun’s rays. The process that transforms sunlight into electricity was discovered as early as 1839 . 
The benefits of solar energy include the relatively low cost for a operative system. Solar systems employ a mature technology and technical expertise and support is global. However, its productivity is dependent on weather conditions and is limited to daylight hours, making it an intermittent source of electricity.
Wind energy (or wind power) refers to the process of creating electricity using the wind, or air flows that occur naturally in the earth’s atmosphere. Modern wind turbines are used to capture kinetic  energy from the wind and generate electricity. It is also considered an intermittent source of renewable energy.
There are three main types of wind energy:
Utility-scale, onshore wind: Wind turbines that range in size from 100 kilowatts to several megawatts, where the electricity is delivered to the power grid and distributed to the end user by electric utilities or power system operators.
Distributed or "small" wind: Single small wind turbines below 100 kilowatts that are used to directly power a home, farm or small business and are not connected to the grid.
Offshore wind: Wind turbines that are erected in large bodies of water, usually on the continental shelf. Offshore wind turbines are larger than land-based turbines and can generate more power.
Offshore Wind Farm
How Wind Turbines Work
When the wind blows past a wind turbine, its blades capture the wind’s kinetic energy and rotate, turning it into mechanical energy. This rotation turns an internal shaft connected to a gearbox, which increases the speed of rotation by a factor of 100. That spins a generator that produces electricity.
The electric generator in a wind turbine is virtually identical to those used in traditional steam-turbine generators with the exception being that the kinetic energy used to rotate the turbine comes from naturally occurring wind forces instead of steam produced by a heat source.  Like solar, the wind doesn’t necessarily blow all the time, making it an intermittent source of power as well.
Rancia 2 geothermal power plant, Tuscany/ Italy
(source: Enel Green Power)
Here on Hawai‘i Island, we have access to a fossil fuel free source of heat that can be used to generate electricity: Geothermal Energy. Use of this heat also eliminates the expense involved with importing those heat generating fuel sources from off-island.
Geothermal energy is the only one of the three options to produce Green H2 we have that can deliver “firm power” or continuous electricity, 24/7/365. With geothermal and the absence of fuel costs, there is also the ability to variably increase output as needed, making it cost effective option for the production of H2 in tandem with providing the ongoing electrical demand for Hawai‘i Island.
Geothermal energy can provide generation level heat consistently, safely, reliably, and for thousands of years. Today’s Geothermal facilities can be engineered to operate with a smaller ecological impact than our current fossil fuel power plants while simultaneously providing portable energy in the form of Hydrogen. These features minimize our overall dependence on imported resources.
Making the Choice
How do we decide what combination of renewable resources to use for power? Do we use just solar, wind, some, or all of the above? How much of a factor should H2 production be given in the overall equation when considering an approach to the future or our energy mix?
Christos Georghiou, Artist
Of course, cost is always a primary concern. However, today, we have more than cost to consider. We have long term sustainability of the systems, themselves, that are critical. We also must consider what our local communities are willing to support (NIMBY)  To answer these questions will take time and a clear understanding of what the lay of the land truly is.
If H₂ is going to be a factor in our decision making, understanding the cost, production capacity and operating efficiency differences between these sources make meaningful impact on the final cost to the community. With intermittent sources of electricity like wind and even more so with solar, continuous production is not possible. Providing that additional capacity beyond normal daily demand growth will require more land dedicated to each of the intermittent sources, thus increasing the initial infrastructure and ongoing operating costs for each.
When considering hydrogen, we must initially decide how we want to use the H2 we produce. How much H2 will we want to produce at the start and in the future? Will it only be produced to for personal transportation or will it be produced to support industrial transportation as well? Will it include production sufficient to supply grid scale supplemental power in the form of fuel cell backup storage? Will it be produced at a scale that can provide for commercial export to other islands? How will we position ourselves for expansion as the need grows? These are questions that, among others, must be weighed, calculated, projected into the future, and serve as the basis for decisions we need to make today that will affect life 20, 40, 60 years from now.
Based on what we currently know, the most economical method for producing hydrogen involves fossil fuels, typically in the form of methane or natural gas and a process known as Steam Methane Reforming (SMR). We also know SMR is not an enduring option for the future. We must produce “Green Hydrogen” which means producing it with renewably generated electricity for electrolysis while using water as the feedstock for the hydrogen. In a perfect world we would want to produce hydrogen 24-7-365 which means that the source for electricity would need to have that capability; rain or shine; day or night.
Of the three options we have, only one has the potential to meet that criteria. However, before that choice can be made, the entire community needs to have an opportunity to evaluate honest, accurate, and complete information upon which to base this kind of decision. Credible information is the key. One additional and important question is: Is this decision something best exclusively left to Hawaiian Electric, governmental agencies and outside companies looking to produce power for Hawai‘i? Do we want to have a seat at the table and be influential enough to have our voices be heard?
Sustainable Energy Hawai‘i is poised gather this information, make it available to both our community and to industry, while organizing forums to openly discuss the economic and social needs with all stakeholders. We trust our community to make wise decisions once we have all the information. We all want the same things for our future. A safe, secure, livable community for all, within which we can share our time with family and friends. Energy, along with food, is considered among the most critical ingredients making up our lives today. Let’s all be a part of the team making the important decisions that will affect all of us down the road.
 S.C. Bhatia, in Advanced Renewable Energy Systems, 2014
 “Kinetic energy” is a form of energy that an object or a particle has by reason of its motion. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.
 Typically, a fossil fuel with the exception of hydroelectric and nuclear generation plants.
 "NIMBY: Not In My Back Yard"