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The search for new sources of power will never end. This topic covers the science, technology and history of various sources of energy like hydro, nuclear, and fossil fuels. it also includes sustainable and renewable power including solar, wind and tidal power. SCIS no. 1933908

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The search for new sources of power will never end. This topic covers the science, technology and history of various sources of energy like hydro, nuclear, and fossil fuels. it also includes sustainable and renewable power including solar, wind and tidal power. SCIS no. 1933908

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Some good information here plus a quiz

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Energy powers buildings, , and transport systems. This is often but can also be like wood and .

Energy use is often measured . Iceland, Canada, the United States and wealthier nations in the Middle East are amongst the highest of energy per capita. Iceland is able to and many Middle Eastern countries have large reserves of oil. Many oil producing countries are also large consumers of oil. It is usually cheaper and more reliable for a country to use their own energy reserves, rather than import resources from elsewhere. Bangladesh, Pakistan and Sri Lanka are amongst the lowest consumers of energy per capita. In Pakistan, around 40 million people don't have access to electricity.

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Energy powers buildings, , and transport systems. This is often but can also be like wood and . Energy use is often measured . Iceland, Canada, the United States and wealthier nations in the Middle East are amongst the highest of energy per capita.

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Scroll down for statistics and renewable energy projects

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Find out about the investment opportunities in New Zealand's renewable energy sector.

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EECA  - Energy Efficiency and Conservation Authority

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EECA  - Energy Efficiency and Conservation Authority

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Has a good diagram of where our energy comes from and scroll down for different types of renewable energy.

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Increasing our supply and use of renewable, low carbon energy is critical in achieving our emissions targets and playing our part to address climate change.

Energy in New Zealand

Energy is required in our day-to-day lives for things such as transport, to power businesses and run our homes. Energy comes from a range of sources - while some of these are renewable, we are still reliant on fossil fuels to produce around 70% of our total consumer energy requirements.

Energy in the future

Explore what our New Zealand Energy Scenario modelling tells us about our potential future energy system.

The video below imagines what the future could look like, based on outcomes modelled from our TIMES-NZ New Zealand Energy Scenarios data. This modelling, which has been developed by EECA in partnership with the BusinessNZ Energy Council (BEC) and The Paul Scherrer Institute, is a technology-based optimisation model that represents the entire New Zealand energy system, encompassing energy carriers and processes from primary resources to final energy consumption.
New Zealand Energy Scenarios interactive data tool

Where our energy comes from

Most of New Zealand's energy is supplied by fossil fuels, including 99% of transport energy, and around 60% of industrial energy. Much or our electricity is generated from renewable energy sources (80-85%), which is promising for reducing our reliance on fossil fuels in the future.

Our large share of renewable electricity is largely due to favourable geography, including being an island nation with mountains, lakes, relatively consistent wind and rainfall, plus access to geothermal resources. The percentage of New Zealand's electricity generated from renewable energy sources varies each year depending on the amount of rainfall, and to a lesser extent, the amount of wind.

Reaching our emissions targets

To reach net-zero carbon emissions by 2050, there is a need to address the 70% of energy currently sourced from fossil fuels. This is important, as about 40% of New Zealand's total greenhouse gas emissions come from energy used for activities such as driving cars and trucks, travelling by plane, burning gas and coal for manufacturing, or creating electricity.

We need businesses to play their part by switching to renewable energy sources where possible. EECA works closely with businesses to help plan their transitions to renewable energy, including providing financial and technical support for decarbonisation projects.
New Zealand's energy-related emissions

What matters in an energy source?

There are a range of factors that can help businesses compare energy sources and understand how useful they are in practice.

Energy return on investment (EROI) - The ratio between the amount of energy required to extract or produce fuel and the amount of useful energy this fuel makes available to deliver other services - such as transport, heat or light. The graph below illustrates the EROI of renewable energy sources commonly used in New Zealand.

Energy return on investment

For an energy source to be useful it needs to deliver significantly more energy than it takes to extract it. If an energy source's EROI number is low it means it is difficult to extract in relation to the output we get from it. If the number is high, it is relatively easy to extract. To be worthwhile, an energy source needs to have an EROI above a range of 7-14.

Historically, fossils fuels have had a high EROI, but as oil and gas resources are depleted, they are becoming more energy-intensive to extract. This means their EROI is decreasing. On the other hand, several renewable energy sources are now on par or better than fossil fuels in terms of EROI. Hydro schemes have a wide range of EROI values because there can be very large differences between hydro schemes in the amount of energy and materials required to construct them, and also in the volume of energy generated due to variances in inflows and hydraulic head.

Data sources and further reading on EROI

Oil and gas

Coal

Hydro

Geothermal

Solar PV

Wind

Biomass (wood)

Demand flexibility as a solution

As New Zealand moves towards achieving 100 percent renewable electricity generation, the challenge of managing renewable energy sources that aren't always available or predictable becomes more pressing. But decarbonising New Zealand's energy system is not just about strengthening renewable energy supply - it will also require addressing increasing energy demand as New Zealand is increasingly electrified.

Enabling demand flexibility means that, in the future, New Zealand households and businesses can help to balance the electricity grid by reducing or increasing their energy use when there is more or less renewable energy available. This prioritises renewable energy use, and ultimately lead to a more sustainable and reliable electricity system.

FlexTalk

To help meet the challenge of increasing demand, EECA has partnered with industry (represented by the Electricity Engineers' Association (EEA)) on the FlexTalk project, which is trialling a communications protocol, OpenADR, to enable actively managed EV charging in real-time New Zealand homes.

This project is an important step in investigating how to integrate demand flexibility within our distribution networks to optimise energy use. Although the scope of this project is for EV charging, the same protocol (OpenADR) may be used in the future to request demand flexibility from other devices such as hot water cylinders and heat pumps.
More about FlexTalk(external link)

Learn about renewable energy sources

Continue reading

Energy's role in climate change

Energy is required in our day-to-day lives for things such as transport, to power businesses and run our homes. While most of our electricity comes from renewable sources, we are still heavily reliant on fossil fuels.
Read more

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Increasing our supply and use of renewable, low carbon energy is critical in achieving our emissions targets and playing our part to address climate change.

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New Zealand Ministry for Culture and Heritage Te Manatu Taonga

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In many ways New Zealand is perfectly placed to develop renewable sources of energy. Its rivers, geothermal springs and pine forests are already producing electricity and heat. In the pursuit of efficient, sustainable energy, the challenge in the 21st century includes harnessing wind and sunlight…

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Choose either Primary or Middle level, then enter the words 'alternative energy', or search for a specific type of energy, like 'solar power'.

Select the articles called alternative energy and solar energy to get a good understanding of this topic.

If the article is too hard or too easy, you can change the Article Reading Level from the top of the page.

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Access to the EPIC resources for schools is restricted for use by staff and students of New Zealand schools. Please refer to Accessing EPIC resources for more information about this.

For EPIC school login queries email epic@dia.govt.nz from your New Zealand school email address.

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Access to the EPIC resources for schools is restricted for use by staff and students of New Zealand schools. Please refer to Accessing EPIC resources for more information about this. For EPIC school login queries email epic@dia.govt.nz from your New Zealand school email address.

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Here you can find comparisons between countries and their use of renewable energy. Scroll down to find informatation on the different types of renewable energy:))

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by Chris Woodford. Last updated: June 2, 2022.

Running low on fuel? Just zip to the gas station and fill up your tank. The only trouble is, you won't be able to do that forever because Earth itself is running low on fuel. Most of the energy we use comes from fossil fuels like oil, gas, and coal, which are gradually running out. Not only that, using these fuels produces air pollution and carbon dioxide-the gas most responsible for global warming. If we want to carry on living our lives in much the same way, we need to switch to cleaner, greener fuel supplies-renewable energy, as it's known. This article is a brief, general introduction; we also have lots of detailed articles about the different kinds of renewable energy you can explore when you're ready.

Photo: Solar energy will come into its own as fossil fuel supplies dwindle and renewables become more economic. But at the moment it supplies only a tiny fraction of world energy. Most of the sun-facing roof of this new school in Swanage, England is covered with 50kW of photovoltaic solar panels (only half of which are shown here). They save around $4000 (£3000) each year in electricity bills-and inspire students to think about where their energy comes from.

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What is renewable energy?

Broadly speaking, the world's energy resources (all the energy we have available to use) fall into two types called fossil fuels and renewable energy:

Fossil fuels are things like oil, gas, coal, and peat, formed over hundreds of millions of years when plants and sea creatures rot away, fossilize, and get buried under the ground, then squeezed and cooked by Earth's inner pressure and heat. Fossil fuels supply about 80-90 percent of the world's energy in most countries (although, as the chart below shows, the amount varies widely from country to country). [1]

Renewable energy means energy made from the wind, ocean waves, solar power, biomass (plants grown especially for energy), and so on. It's called renewable because, in theory, it will never run out. Renewable sources currently supply about 10-20 percent of the world's energy.

What's the difference between fossil fuels and renewable energy?

In theory, fossil fuels exist in limited quantities and renewable energy is limitless. That's not quite the whole story, however.

The good news is that fossil fuels are constantly being formed. New oil is being made from old plants and dead creatures every single day. But the bad news is that we're using fossil fuels much faster than they're being created. It took something like 400 million years to form a planet's worth of fossil fuels. But humankind will use something like 80 percent of Earth's entire fossil fuel supplies in only the 60 years spanning from 1960 to 2020. When we say fossil fuels such as oil will "run out," what we actually mean is that demand will outstrip supply to the point where oil will become much more expensive to use than alternative, renewable fuel sources.

Just as fossil fuel supplies aren't exactly finite, neither is renewable energy completely infinite. One way or another, virtually all forms of renewable energy ultimately come from the Sun and that massive energy source will, one day, burn itself out. Fortunately, that won't happen for a few billion years so it's reasonable enough to talk of renewable energy as being unlimited.

Fossil fuels versus renewables

Different countries get their energy from different fuels. In the Middle East, there's more reliance on oil, as you'd expect, while in Asia, coal is more important. To keep things in perspective, it's worth noting that hardly any countries use more than 20 percent renewable energy. Nations like Brazil and Norway score highly because they make great use of hydroelectricity.

Chart: Percentage of energy supplied by renewables and hydroelectricity in 2021 for 10 example countries. The world average is shown by the black bar in the center. Green-colored countries are better than average; red-colored countries are worse. Source: BP Statistical Review of World Energy 2021.

In the United States, the breakdown looks like this:

Chart: Percentage of total US energy supplied by different fossil fuels and renewables in 2020. Source: Office of Coal, Nuclear, Electric and Alternate Fuels, Energy Information Administration, US Department of Energy. Data published April 2021. Note that figures are individually rounded and may not add to 100%.

From the pie chart, you can see that about 80% of US energy still comes from fossil fuels (down from 84% in 2008 and virtually unchanged since 2014), while the remainder comes from renewables and nuclear. Looking at the renewables alone, in the bar chart on the right, you can see that wind, hydroelectric, and biomass provide the lion's share. Wind and solar provide just 37 percent of US renewable energy and are steadily increasing in importance: solar currently provides 11 percent of total US renewable energy (up from 4 percent in 2014), while wind provides 26 percent (up from 18 percent in 2014). That doesn't sound too bad, but remember that renewables make up just 12 percent of all our total energy use. So solar provides about 1.3 percent of the total energy (11 percent of 12 percent) and wind provides about 3.1 percent (26 percent of 12 percent). Renewables have increased from 7% to 12% of the total since 2008, which is a much bigger increase than it might sound. But don't forget the bottom line: 80 percent of our energy-the vast majority-is still coming from fossil fuels.

Please note that these charts cover total energy and not just electricity.

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What are the different types of renewable energy?

Almost every source of energy that isn't a fossil fuel is a form of renewable energy. Here are the main types of renewable energy:

Solar power

For as long as the Sun blazes (roughly another 4-5 billion years), we'll be able to tap the light and heat it shines in our direction. We can use solar power in two very different ways: electric and thermal. Solar electric power (sometimes called active solar power) means taking sunlight and converting it to electricity in solar cells (which work electronically). This technology is sometimes also referred to as photovoltaic (photo = light and voltaic = electric, so photovoltaic simply means making electricity from light) or PV. Solar thermal power (sometimes called passive-solar energy or passive-solar gain) means absorbing the Sun's heat into solar hot water systems or using it to heat buildings with large glass windows.

Wind power

Photo: This relatively small wind turbine, in Staffordshire, England makes up to 225kW of electricity, which is about enough to power 100 electric kettles or toasters at the same time. The world's most powerful wind turbines can make a maximum of about 13 megawatts (13,000 kilowatts), which is about 60 times as much as this one.

Depending on where you live, you've probably seen wind turbines appearing in the landscape in recent years. There are loads of them in the United States and Europe, for example. A turbine is any machine that removes kinetic energy from a moving fluid (liquid or gas) and converts it into another form. Windmills, based on this idea, have been widely used for many hundreds of years. In a modern wind turbine, a huge rotating blade (similar to an airplane propeller) spins around in the wind and turns an electricity generator mounted in the nacelle (metal casing) behind. It takes roughly several thousand wind turbines to make as much power as one large fossil fuel power plant. Wind power is actually a kind of solar energy, because the winds that whistle round Earth are made when the Sun heats different parts of our planet by different amounts, causing huge air movements over its surface.

Hydroelectric power

Hydro means water, so hydroelectricity means making electricity using water-not from the water itself, but from the kinetic energy in a moving river or stream. Rivers start their lives in high ground and gradually flow downhill to the sea. By damming them, we can make huge lakes that drain slowly past water turbines, generating energy as they go. Water wheels used in medieval times to power mills were an early example of hydro power. You could describe them as hydromechanical, since the water power the milling machines used was transmitted by an elaborate systems of wheels and gears. Like wind power, hydroelectric power is (indirectly) another kind of solar energy, because it's the Sun's energy that drives the water cycle, endlessly exchanging water between the oceans and rivers on Earth's surface and the atmosphere up above.

Ocean power

Photo: A model of an OTEC (ocean thermal energy conversion) plant that makes energy using temperature differences between different layers of ocean water. Photo by Warren Gretz courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).

The oceans have vast, untapped potential that we can use in three main ways: wave power, tidal barrages, and thermal power.

Wave power uses mechanical devices that rock back and forth or bob up and down to extract the kinetic energy from moving waves and turn it into electricity. Surfers have known all about wave power for many decades!

Tidal barrages are small dams built across estuaries (the points on the coast where rivers flow into the sea and vice versa). As tides move back and forth, they push huge amounts of water in and out of estuaries at least twice a day. A barrage with turbines built into it can capture the energy of tidal water as it flows back and forth. The world's best-known tidal barrage is at La Rance in France; numerous plans to build a much bigger barrage across the Severn Estuary in England have been outlined, on and off, for almost a century.

Thermal power involves harnessing the temperature difference between warm water at the surface of the oceans and cold water deeper down. In a type of thermal power called Ocean thermal energy conversion (OTEC), warmer surface water flows into the top of a giant column (perhaps 450-1200m or 1500-4000ft tall), mounted vertically some miles out to sea, while cooler water flows into the bottom.[2] The hot water drives a turbine and makes electricity, before being cooled down and recycled. It's estimated that there is enough thermal energy in the oceans to supply humankind's entire needs, though little of it is recovered at the moment.

Biomass

Biomass is a fashionable, fancy word that really just means plants (or other once-living things) used as fuel (especially ones grown specifically for that reason). Wood fuel gathered by people in an African country is biomass; biofuels such as ethanol, used to make diesel for car engines, is also biomass; and chicken manure used to fire power plants is biomass too. The great thing about biomass is that it's a kind of renewable energy: plants grow using sunlight, which they convert into chemical energy and store in their roots, shoots, and leaves. Burning biomass releases most of that energy as heat, which can we use to warm our homes, generate electricity, and fuel our vehicles.

Chart: Biomass (including wood) supplied about 39 percent of the renewable energy (18% + 21% in the chart higher up the page) used in the United States in 2020 and 5 percent of the total energy (39 percent of the 12 percent total energy that renewables contribute). Although you might expect most of it comes from wood, quite a lot comes from biofuels (mostly ethanol) as well. Biomass supplied 45 percent of the USA's total renewable energy in 2018, though the proportion has fallen significantly since then due to the huge growth in solar and wind. Data from US Office of Energy Administration, 2021.

Biomass is more environmentally friendly and sustainable than fuels such as coal for three main reasons.

1. Unlike coal (which takes many millions of years to form from plant remains), biomass can be produced very quickly and we can easily grow new plants or trees to replace the ones we cut down and burn (in other words, biomass can be genuinely sustainable).

2. Plants absorb as much carbon dioxide from the air when they grow as they release when they burn, so in theory there is no net carbon dioxide released and burning biomass does not add to the problem of global warming. (That's why biomass is sometimes called a carbon neutral form of energy.) I say "in theory" because in practice growing, harvesting, and transporting biomass may use energy (tractors or trucks running on oil might well be involved, for example) and thatreduces the overall environmental benefit. Also, new young trees don't absorb as much carbon dioxide as the older trees that are cut down.

3. Biomass is often simply wasted or sent to landfill. Burning something like waste wood offcuts from a lumber yard or chicken manure from a poultry factory not only gives us energy, it also reduces the waste we'd otherwise need to dispose of.

What is a biomass furnace?

Photo: Stoves have evolved quite a bit, but they haven't changed all that much over the years. Modern woodburners produce less indoor pollution than old stoves, but they still throw significant amounts of pollution outside.

People tend to burn biomass in two ways. The simplest method is to use a wood-burning stove, an enclosed metal box made from something like cast iron, with opening doors at the front where the fuel is loaded up and a small chimney called a flue to carry away carbon dioxide, smoke, steam, and so on. This generally provides heat in a single room, much like a traditional coal fire.

A biomass furnace is a more sophisticated option that can heat an entire building. Unlike a wood-burning stove, a biomass furnace does the same job as a central-heating furnace (boiler) powered by natural gas, oil, or electricity: it can provide both your home heating and hot water and it can even power modern underfloor central heating. It's not like a dirty and labor-intensive coal-fire and doesn't require huge amounts of starting up, cleaning, or maintenance. All you have to do is load in your biomass (generally, you'd use wood pellets, wood chips, chopped logs, cereal plants, or a combination of them) and periodically (typically every 2-8 weeks, depending on the appliance) empty out the ash, which you can recycle on your compost.

Photo: This large biomass generator turns woodchips into electricity. Photo by Jim Yost courtesy of US Department of Energy/NREL.

While wood-burning stoves have to be manually filled up with logs, biomass furnaces are often completely automated: they have a large fuel hopper on the side that automatically tops up the furnace whenever necessary. Unlike with a coal fire, you don't have to mess around trying to get the fuel lit: biomass furnaces have simple, electric ignition systems that do it all for you. It's perfectly possible to run a system like this all year round, but in summertime when you don't need home heating it might be excessive to have your furnace running purely to make hot water. Many people switch off their furnaces entirely for the summer months, relying on solar thermal hot water systems (glass panels on the roof that warm up water using the Sun's heat), electrical immersion heaters (a heating element fitted inside a hot water tank), or an electric shower to tide them through until fall or winter. It's perfectly possible to couple together a biomass furnace with a solar hot-water panel so the furnace switches on when the panel can't produce enough hot water for your needs.

Photo: Biomass furnaces scale up very well: this is a 50megawatt power plant in Burlington, Vermont that produces electricity for local people using wood fuel. Photo by Dave Parsons courtesy of US Department of Energy/NREL.

Biomass furnaces and wood-burning stoves are generally considered to be far more environmentally friendly than home heating systems powered by fossil fuels, but one drawback is worth bearing in mind: burning biomass is cleaner than burning coal but still produces air pollution. If you're considering buying a biomass stove or furnace, ask about emissions (sales brochures usually mention how much dust, carbon monoxide, and oxides of nitrogen appliances produce); and be sure to find out whether there are pollution or other planning restrictions in your area before you commit yourself to an expensive purchase. And as with any form of home heating that involves burning fuel, be absolutely sure to install a carbon monoxide detector for your own safety: badly ventilated heating appliances can kill, whether they're environmentally friendly or not!

Geothermal energy

Photo: A geothermal electricity generator in Imperial County, California. Photo by Warren Gretz courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).

Earth may feel like a pretty cold place at times but, inside, it's a bubbling soup of molten rock. Earth's lower mantle, for example, is at temperatures of around 4500°C (8000°F). It's relatively easy to tap this geothermal (geo = Earth, thermal = heat) energy using technologies such as heat pumps, which drive cold water deep down into Earth and pipe hot water back up again. Earth's entire geothermal supplies are equivalent to the energy you could get from about 25,000 large power plants![3] The amount of this we might actually recover is more like 70-80 gigawatts (70,000-80,000 megawatts), which is about 50 of the same power plants.[4]

Nuclear fusion

Conventional nuclear energy is not renewable: it's made by splitting up large, unstable atoms of a naturally occurring chemical element called uranium. Since you have to feed uranium into most nuclear power plants, and dig it out of the ground before you can do so, traditional forms of nuclear fission (the scientific term for splitting big atoms) can't be described as renewable energy. In the future, scientists hope to develop an alternative form of nuclear energy called nuclear fusion (making energy by joining small atoms), which will be cleaner, safer, and genuinely renewable.

Fuel cells

If you want to use renewable power in a car, you have to swap the gasoline engines or diesel engine for an electric motor. Driving an electric car doesn't necessarily make you environmentally friendly. What if you charge the batteries at home and the electricity you're using comes from a coal-fired power plant? One alternative is to swap the batteries for a fuel cell, which is a bit like a battery that never runs flat, making electricity continuously using a tank of hydrogen gas. Hydrogen is cheap and easy to make from water with an electrolyzer. Fuel cells are quiet, powerful, and make no pollution. Probably the worst thing they do is puff steam from their exhausts!

How can New York City go renewable?

Talking about "renewable energy" can be very abstract. It sounds great in theory, and no-one would disagree with using more environmentally friendly forms of power, but what would it actually mean in practice? Suppose I make you Mayor of New York City (NYC) for a week and we agree that your top priority is to figure out how to power the entire city with renewable energy. How are you going to deliver eco-friendly electricity to one of the world's biggest cities?

How much energy do we need?

First off, you'll need to know how much energy the city uses. The amount is going to go up and down and you'll need to be able to meet huge peaks in demand as well as day-to-day, average power. But let's just worry about the average power for now. A quick bit of searching reveals that NYC's average power demand is of the order of 5 gigawatts [Source: Accent Energy]. It may be more or less, but for this exercise it really doesn't matter.

What does 5 gigawatts actually mean? 5 gigawatts is the same as 5,000 megawatts, 5 million kilowatts, or 5 billion watts. A big old-fashioned ( incandescent) lamp uses about 100 watts, so NYC is consuming the same amount of energy as 50 million of those lamps glowing at the same time. If you prefer, think of an electric toaster, which uses about 2500 watts. NYC is like 2 million toasters burning away all at once-a line of toasters stretching 500 km (roughly 300 miles) into the distance! It sounds like we're talking about an awful lot of energy!

How do we make that much energy right now?

And yet... five gigawatts is actually not as much as it sounds. A big, coal-fired power plant could make about two gigawatts, so you'd need about 3 coal stations to power the city (4 to be on the safe side). Nuclear plants typically produce less (maybe 1-1.5 gigawatts), but a big nuclear station like Indian Point (just outside NYC) can make two gigawatts. So going nuclear, you could manage with perhaps 3-6 good-sized plants. See how easy it is to power a city the old way? You only need a handful of big old power plants.

Artwork: It takes about 1000 wind turbines (1000 small blue dots), working at full capacity, to make as much power as a single coal-fired power plant (one big black dot).

How could we make that much energy with renewables?

This is where it starts to get tricky. Let's say you're keen on wind turbines. Great! How are you going to power NYC with wind? We need 5 gigawatts of power and a modern turbine will deliver about 1-2 megawatts when it's working at full capacity. So you'll need a minimum of 2500-5000 wind turbines-and an awful lot of land to put them on. Is it doable? One of the world's biggest wind farms, at Altamont Pass in California, has almost 5000 small turbines and produces only 576 megawatts, which is about 11 percent of what we need for NYC. Now these are mostly old turbines, they're really quite puny by modern standards, and we could certainly build much bigger and more powerful ones-but, even so, powering NYC with wind alone seems to be a fairly tall order.

What about solar power? For simplicity, let's assume NYC is full of ordinary houses (and not huge skyscrapers). Cover the roof of a typical house with photovoltaic ( solar-electric) panels and you might generate 5 kilowatts (5,000 watts) of power; stick those panels on a larger, municipal building and you might get three or four times as much. Let's assume every building could make 10 kilowatts for us. To generate 5 gigawatts, we'd need 500,000 buildings generating electricity all the time. That sounds like another tall order.

What other options do we have? How about harnessing the tidal power of the East River? That's been done already: six turbines installed between 2006 and 2008 produce, altogether, about 200 kilowatts of the power used in Manhattan. [Source: Tidal Turbines Help Light Up Manhattan, MIT Technology Review, April 23, 2007.] That's a good start, but we'd need something like 140,000 of these turbines to generate our 5 gigawatts! There simply isn't enough power in the river.

Gulp. None of this is meant to put you off renewable energy; as far as I'm concerned, the world can't get away from fossil fuels fast enough. But looking at the science and the numbers, it's clear that if we're going to use renewables, and only renewables, we need an awful lot of them. Switching to renewables means building many thousands (and maybe hundreds of thousands) of separate power-generating units.

How you can use more renewable energy

Chart: World consumption of renewable energy is currently growing at about 16-17 percent per year. Chart drawn using data from BP Statistical Review of World Energy 2021 (and earlier editions for older data).

If you want to make a difference to the planet by making more use of renewable energy, what's the best way to do it? Given that you spend quite a lot of the money you earn on energy, try to direct that money where it will have the biggest effect. Here are some simple tips:

Switching supplier

If you get most of your energy from electricity, you can switch supplier (or tariff) to one that uses more renewable power. Sometimes this is less effective than it sounds. If your supplier mainly operates hydroelectric power plants and you switch from its ordinary power tariff to a green tariff, will you actually be increasing the amount of green power in the world or simply paying the company more money for doing exactly the same as it was doing before? A better option is to switch to a smaller supplier building new wind turbines or solar plants. That way, you'll be helping the company to invest in more renewable energy and helping to switch the world away from fossil fuels.

Making your own power

If you have more money to spend, you could investigate making some of your own energy by installing something like photovoltaic solar panels, a solar hot water system, or a ground-source heat pump. Since you'll be using less energy from utilities, making power this way saves money and helps the environment too. Although making your own power pays for itself eventually, the initial investment in turning your house into an eco home can be costly. But, do your homework, and you have the reassurance of knowing that the money you're spending is helping to reduce your own use of fossil fuels.

Using more by using less

The easiest way to save the planet is to use resources more wisely. If you can't find a way to use more renewable energy, you can still try to use less conventional energy (from fossil fuels). Being more efficient is surprisingly quick and easy and often costs nothing at all. It costs nothing, for example, to share your car with a friend and getting a bus or a train often saves you money, as well as saving energy. Heat insulating your home is another good way of saving energy (and money) at little or no cost, while turning down your thermostat (and putting on an extra layer of clothing) is something anyone can do without spending so much as a cent. Try switching to energy-efficient light bulbs (LEDs are more efficient than CFLs and now just as cheap) and use energy monitors to help you measure and cut the cost of your other appliances. You can save money in your car too by giving some thought to fuel efficiency.

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On this website

Books

General

Renewable energy by Bruce Usher. Columbia University Press, 2019. A concise, balanced, up-to-date primer for non-technical readers.

The Switch by Chris Goodall. Profile, 2016. An optimistic look at why it makes economic sense to switch from fossil fuels to solar power.

Homeowners' Guide to Renewable Energy by Dan Chiras. New Society, 2011. A more practical guide that reviews and compares different renewable energy approaches, including solar, wind, and biomass. Chapter 6 (Wood Heat) covers retrofitting fireplaces, wood-burning stoves, pellet stoves, and masonry heaters.

Sustainable Energy-Without the Hot Air: An excellent online (and printed) book by Cambridge physicist David MacKay, who considers how we can meet our energy needs in the future without fossil fuels. Can we really supply all the energy we're going to need just from renewables? Prof MacKay's examples all come from the UK, where he lives, but his basic arguments apply worldwide.

Fueling our Future: An Introduction to Sustainable Energy by Robert L. Evans. Cambridge University Press, 2014. Covers similar ground to David MacKay, but without the same scientific approach.

Textbooks

Renewable Energy Resources by John Twidell and Tony Weir. Routledge, 2015. A comprehensive guide to all the different kinds of renewable energy with lots of suggestions for further reading.

Renewable Energy by Godfrey Boyle. OUP, 2012. A good, solid text for undergraduates and others studying energy topics.

Practical guides

For younger readers

How Renewable Energy Works by Geoff Barker. Franklin Watts, 2017/Gareth Stevens, 2014. A simple, 32-page illustrated run-through of the basic kinds of renewable energy. Ages 8-10.

Renewable Energy: Discover the Fuel of the Future With 20 Projects by Joshua Sneideman. Nomad, 2016. A great hands-on introduction to green energy, with a selection of well-conceived activities. Ages 9-12.

Doable Renewables: 16 Alternative Energy Projects for Young Scientists by Mike Rigsby. Chicago Review Press, 2010. Another great hands-on guide with more challenging and detailed experiments than the book above and aimed at a slightly higher age range (10+).

Energy by Chris Woodford. New York/London, England: DK, 2007. My own, more general introductory book about energy compares all the different forms of renewable and fossil energy. Suitable for ages 8-12.

Articles

References

1. ↑ See "Primary energy: Consumption by fuel" in BP Statistical Review of World Energy 2021, p.11.

2. ↑ 450-1200m is the sort of range quoted for OTEC plants in Ocean Energy Tide and Tidal Power by R. H. Charlier, Charles W. Finkl, Springer, 2009, p.14.

3. ↑ This is based on 1500 megawatt power plants and an estimated figure for Earth's total surface flow of 42 million megawatts, which comes from "Chapter 1: A Global Assessment of Geothermal Resources" by Marek Hajto et al inGeothermal Water Management by J. Bundschuh et al, CRC Press, 2018, p.3.

4. ↑ The 70-80GW figure comes from theWorld Bank, althoughGeothermal Water Management by J. Bundschuh et al, CRC Press, 2018, p.19 suggests the maximum figure could be double this (140GW).

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More to explore on our website...

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Introduction to renewable energy | Types of renewable energy

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An easy-to-follow introduction to renewable energy. Introduces the main types of renewables and explains how you can use more green energy.

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Renewable energy is fuel that comes from a source that can be replenished in a short amount of time. This includes solar, wind, water, geothermal power and bioenergy. While renewable energy sources may not always be available - for example, if there is no wind to drive wind turbines, or cloudy days that reduce solar energy - they play an important part in reducing the use of non-renewable resources. Furthermore, many of these resources do not emit greenhouse gases directly into the atmosphere.

Solar power

In the broadest sense, solar power supports all life on Earth and is the original source for all other energy resources we use. Solar energy is the Sun's rays (solar radiation) that reach the Earth.

Having produced solar radiation for millions of years through nuclear fusion, this powerhouse produces so much energy that the amount of sunlight that reaches the Earth in a single hour could meet the energy demands of the whole world for an entire year! Outside Earth's atmosphere, the Sun's energy contains about 1,300 watts per square metre. About one-third of this light is reflected back into space, and some is absorbed by our atmosphere. Solar energy can be used directly to heat water or spaces (a greenhouse, for example).

In this process, the energy in the form of solar radiation is converted into thermal or heat energy. Solar energy can also be transformed into electricity through photovoltaics or solar power plants.

With such an amazing power source that produces no air pollution, you may be asking yourself why we do not utilise it more. The problem lies in our ability to harness the Sun's power efficiently. At the moment, solar panels that capture sunlight and turn it into energy are expensive to produce and inefficient, but technology is improving. New Zealand does not yet have any solar-powered power stations.

Explore solar power further.

Wind power

People have been using wind for hundreds of years to transform the wind's kinetic energy into mechanical energy that drives machines, mills grain and pumps water.

Modern technology wind mills use the wind to drive blades that turn generators that produce electricity. Wind power is hailed as a 'green' technology as it produces no air pollution. However, wind farms need a lot of wind turbines to be efficient, opponents complain about the noise, some people think they are eyesores, and there are fears that large wind turbines could be endangering wild bird populations.

New Zealand has some areas with consistent and strong wind levels, for example, in the Manawatu. This provides prime conditions for wind farming - indeed, New Zealand already has a number of wind farms supplying our electricity.

Explore wind power further.

Hydro (water) power

Like wind power, hydro power has been used to generate power for a long time - the Egyptians were using hydro power 2,000 years ago to mill grain. Hydro power is the most common form of renewable energy to generate electricity. It is estimated that around 70-80 percent of New Zealand's electricity supply is generated through hydro power.

The movement of water on Earth that fills the rivers and subsequently drives hydro power is due to the water cycle. To use the power of water, it is often stored in dams and then channelled through pipes that drive the turbines of a generator.

The benefits of storing water in dams for hydro power include areas for water sports and recreation. However, the modification of rivers can damage the ecology of an area, for example, interfering with fish migration. Now, any proposed hydro power schemes must take into account the ecological and local impacts they might have.

Explore hydro power further.

Geothermal power

Geothermal energy is derived from heat retained inside the Earth. To use this heat, we need a fluid that transports the heat (steam or water). The fluid needs to be able to move through pores and cracks in the Earth's crust. When a source of heated fluid is close enough to the Earth's surface, wells can be drilled into the ground to transport the geothermal fluid up.

In New Zealand, there are several low and high temperature geothermal fields, the most famous area being the Taupo Volcanic Zone where the geothermal reservoir reaches temperatures between 200-340°C. There are a few technologies used. Most commonly, the water or steam is heating a secondary fluid in a power station, which drives generators to produce electrical power.

Side effects of geothermal power are mostly related to what is being done with the water or steam after it has been removed from the ground. Geothermal power plants generate CO ₂ - but far less than fossil fuelled plants.

Explore geothermal power further.

Bioenergy

Bioenergy means converting biomass to produce a form of energy like heat, light, electrical power or transport fuel. Burning wood in a fire, for example, is using bioenergy. Natural materials that are used as energy sources can be wood, plants and even bacteria.

With rising oil prices and concerns about how long fossil fuels will be available, bioenergy has received a lot of attention in recent years as people search for alternatives like using the by-products from sawmills, re-using cooking oils and planting fast growing plants that can be converted into a usable fuel. While these resources are renewable, they produce greenhouse gases.

Explore New Zealand's bioenergy options further.

Useful links

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Renewable energy is fuel that comes from a source that can be replenished in a short amount of time. This includes solar, wind, water, geothermal power and bioenergy. While renewable energy sources may not always be available - for example, if there is no wind to drive wind turbines, or cloudy days that reduce solar energy - they play an important part in reducing the use of non-renewable resources.

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There are some cool videos here - check out Out geothermal energy works in Iceland or how wind turbines work...