Introduction to Renewable Energy

Introduction to Renewable Energy

E Nehrenheim, Ma¨lardalen University, Va¨stera˚s, Sweden

ã 2014 Elsevier Inc. All rights reserved.

Introduction – What is Renewable Energy? 1

Utilizing Energies 1

Fuels 1

Biofuels 2

Introduction – What is Renewable Energy?

Renewable energy, in contrast to so called fossil energy, or fossil fuels, is renewable within our generation time. Fossil fuels are

distinguished from renewable sources of energy by the time it takes for the energy to be transformed to its final application. Oil,

coal and natural gas were slowly formed by the degradation of organic matter in prehistoric times, which defines them as

non-renewable, or fossil. Peat was long considered renewable but we now know that peat is formed over a period of 10 000

years h. In contrast to this, solar energy can be transferred directly to electricity. Waves and wind power have similar advantages - the

energy is formed and delivered on a grid without consuming any earth resources.

In recent years, efforts to find replacements for fossil fuels have increased slowly but surely. In the late twentieth century peak oil

production was the focus of most energy development. The prognosis of when oil production will decline has varied significantly

and lately the alarm has been given little attention. Climate change, on the other hand, has been one of the major forces for the

promotion of renewable energy and CO2 politics in general. Net zero CO2 energy sources, CO2 capture and storage and energy

efficiency have all been high on the agenda of global opinion. Climate change is the most commonly debated and well known

environmental topic today. Climate change is caused by a combination of natural and anthropogenic factors that slowly increase

the temperature in the atmosphere. Pollution that causes global warming is constantly measured and all climate change affecting

gases are given in equivalents of CO2. Some renewable energy processes (if the production of the system is not accounted for) are

completely CO2 neutral, including solar, wind and wave energy.

Renewable energy, just as fossil energy, is used for electricity production, heat production and as vehicle fuels. Common for all

renewable energy sources is their recent rapid development and it can be assumed that the different technologies will continue to

develop far into our future. In recent years, the change to renewable energy has enabled the development of new energy and CO2

capturing technologies and increased their feasibility, for example, algae cultivation.

Renewable energies can be roughly subdivided into energies and forces to be utilized and burnable fuels and gases. Some examples

are given below, but these represent only a snap shot of the current status, as the trend towards renewable energy implementation

has been developing rapidly in recent years

Utilizing Energies

Solar energy (solar panels and solar cells) is direct use of the radiation coming from the sun. This energy has always been used in the

undeveloped world for heat, especially cooking water.

Wind energy, or wind power, is another very old technology. The word windmill stems from the tradition of using wind driven

‘machines’ where blades rotated by the force of wind and the power was used for milling grains. Similarly, wind pumps used the

wind for pumping water. Nowadays, windmills are often connected to a turbine for generating electricity.

In the large oceans of the world water is moved due to temperature changes, salt balances and gravity. The forces generated have

been used for utilization of energy. Ocean energy technology uses the forces of the waves. In its simplest form a floating device is

connected to a generator on the bottom of the sea. From that, many highly advance technologies have been developed to utilize the

force of the oceans in a safe, efficient and sustainable way.

Fuels

Hydrogen is a powerful source of energy, used by NASA to fuel rockets since the 1970s. Hydrogen can be reclaimed from

hydrocarbons such as natural gas (most common) or extracted from water in electrolysis by using electrical current. Some

researchers have shown that microorganisms can form hydrogen, but so far few feasible projects are known.

Geothermal heat is common in countries such as Iceland, where the heat is easily accessible. Deep boreholes are also applicable

and heat pumps can bring even low temperature heat in enough quantity to warm individual houses.

Reference Module in Earth Systems and Environmental Sciences http://dx.doi.org/10.1016/B978-0-12-409548-9.09138-7 1