Global energy consumption refers to the amount of energy consumed during industrial activities such as processing products and during operations of machines and vehicles. Global energy consumption is basically measured in terms of the amount of energy harnessed annually from each source for use in human activities across all industrial sectors ( Sutherland et al., 2014) . It excludes energy obtained from consumption of food products and those resulting from burning of biomass. Organizations such as the International Energy Agency (IEA) and the European Environment Agency (EEE) provide the data regarding global energy consumptions on annual basis. According to estimates by the Energy Information Administration (EIA) in 2013, the Total Primary Energy Supply (TPES) was approximately 13,541 Mtoe. Between 2000 and 2012, coal was the most commonly used form of energy. There was also an increased growth in the use of oil and natural gas as forms of energy, as well as hydroelectric power ( Ürge-Vorsatz et al., 2015) . The current global demands for energy and the impacts of non-renewable energy sources on the environment as well as the existence of alternative renewable energy sources have resulted in the need to determine their viability in achieving sustainability of energy supply globally. This paper examines the current trends in energy consumption globally, the need for renewable energy sources, and the different forms of renewable energy that can be harnessed to achieve the global energy needs.
Global energy consumption has increased by 0.1% since 2015 at the same rate as the growth in energy demands. In 2008, it was estimated that the global consumption of energy was 132,000 terawatt-hours (TWh) the consumption of energy has increased considerably in the G20 countries which account for 5% of the global energy consumption ( Hall et al., 2014) . In 2009, there was a decline in the global energy consumption by 1.1% due to the financial and economic crises. Consumptions of energy have been highest in China, the United States and Eurasia that constitutes more than half of the global energy demands. Oil is the most commonly used fuel and accounts for 32.9% of the global energy demands. Developing economies presently account for 58% of the global energy use (Nejat et al., 2015). The price of most non-renewable sources of energy such as oil has remained high in the past years with oil being sold averagely at $52.39 per barrel. Global oil consumption has grown by 1.9 million barrels per day since 2014. China accounts for the largest user of oil with a consumption of 770,000 barrels a day.
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Natural gas is another commonly used form of energy globally with a growth of 1.7% used in 2014, the US and Norway were top two countries with an increase in demand for Natural gas by 5.4% and 5.5% respectively. The shipments of pipelines for the production of natural gas increased by 4% in 2014 resulting in a growth in pipeline exports from Russia. Coal consumption in 2014 grew by 1.8% in the United States but declined by 1.5% in China. Global hydroelectric output increased by 1.3% in China and accounted for virtually all the increases. The production of carbon dioxide due to industrial activities utilizing fossil fuels increased by 0.1% in 2015. In addition to the recession that occurred in 2009, this was the lowest growth rate in a period of 20 years. This was contributed to by the focus on reduced consumption of energy and a shift to the use of renewable forms of energy which are used in place of fossil fuels. There is presently a concern regarding the impacts of global warming emissions due to different sources of energy. Efforts that have been put in place to address this situation include the Kyoto Protocol, which represents an agreement by the United Nations (UN) to reduce the impacts on climate due to the emission of gasses which accumulate in the atmosphere, causing an increase in global temperatures ( Sutherland et al. 2014) . The most commonly produced greenhouse gasses include sulfur dioxide, nitrous oxides, and particulate matter which are emitted from the combustion of fossil fuels and biomass.
The demand for renewable energy sources has been attributed to the fact that non-renewable energy sources are expensive to use and have a negative impact on the environment. For instance, non-renewable energy sources such as oil and natural gas have an impact on the environment upon the use of their products, they undergo depletion, they require expensive investments to use, and they contribute to global greenhouse effects ( Hall et al. 2014) . This is counterproductive to the efforts by various stakeholders towards enhancing the growth of different sectors of the economy that require alternative energy sources. For example, the growth in the retail industry such as the growth of supermarkets, wholesale companies, and information technology organizations that need clean energy for their operational activities. This has resulted into increased need to make use of renewable energy sources. In the foods, drinks, and pharmaceutical industries, there has been the need to be involved in the use of energy sources that have the least impact on the environment ( Ürge-Vorsatz et al., 2015) . A switch to renewable sources of energy is part of the overarching strategies of achieving sustainability. The health care industry also involves operational activities that involve the use of fossil fuels, and this has a negative impact on the environment and related health problems worldwide ( Nejat et al., 2015) . Additionally, the growth of cloud computing is one of the contributing factors to increased consumption of electricity. Similarly , finance, professional services, logistics, and real estate sectors have contributed to increased energy consumptions due to the use of electricity in lighting electronic devices, heating, and cooling offices. The increased use of green power options has been achieved by the purchase of renewable energy certificates leading to an increase in the use of renewable sources of energy by companies in need to enhance a reputation of responsible use of energy and being leaders in the prevention of climate change.
Thre are different types of renewables energy sources that can be put in place to cater for the extra global energy demands caused by urbanization and industrialization. First, hydroelectric power is the oldest and largest form of renewable energy and constitutes 10% of the energy use in the United States. Hydroelectric power plants have the ability to convert water energy into electricity ( Fettweis & Zimmermann, 2008) . This is basically achieved by constructing dams across rivers resulting into the water a reservoir which is released to turn turbines that produce electricity. It is recommended because it does not produce emissions into the atmosphere despite the ecological impact on quality of aquatic life caused by the act of dam constructions.
Biomass is the second most commonly used form of renewable energy in the production of electricity. It has a capacity to produce 7,000 MW in the United States. Biomass is composed of organic and industrial wastes and can be burnt in specially designed power plants. When burnt, it produces a low amount of sulfur dioxide. It can also be used indirectly when it produces methane gas that decays in a process of gasification. Methane has the ability to produce power when it is burnt in a boiler to produce steam that can be used to turn steam turbines or through the operation of internal combustion engines ( Carrasco et al. 2006) .
Thirdly, we have geothermal energy. This is a form of power that utilizes high-temperature steam in turning turbines that enable the production of electricity. Geothermal power plants have the ability to draw steam from underground reservoirs or have the ability to heat water by pumping it into a hard surface such as a rock. Drilling of wells is done to access to high-temperature steam from the ground. Compressor pumps are then used to pump steam out of the earth ( Fettweis & Zimmermann, 2008) . The energy pumped into and out of the earth is in a renewable form because it can be replaced by the cycle of seasons.
Solar energy is another form of renewable energy generated by harnessing of the light rays from the sun to produce electricity, heat, and light. The use of photovoltaic cells (PV) enables conversion of sunlight to electricity using solar cells. It is more recommended for use in meeting residential electricity needs. The heat of the sun is used in an active or passive manner. The increase in technology in the production of solar panels and their availability in retail businesses provide energy users with the opportunity to harness it in energy needs in industries, homes, and offices ( Carrasco et al. 2006) .
Another type of renewable energy is wind power, and it is generated when installed turbines are turned by strong winds. The hub of the windmill is connected to a shaft that turns a generator. Most wind turbines range in sizes of the amount of power they produce from 50 kilowatts to 4 megawatts. The turbines, no matter the size, generates adequate energy to meet domestic consumption needs. The occurrence of winds in different parts of the world such as in arid areas provides suitable locations for the installation of this form of energy plants. In the United States, it is estimated that wind energy can contribute to the production of 6000 MW of power which can provide electricity to 1.5 million homes ( Carrasco et al. 2006) .
Lastly , Hydrogen fuel cells, although not exclusively renewable forms of energy, they are highly abundant and have very low pollution capacities when used. Hydrogen can undergo combustion as a fuel in vehicles, producing water as the only product ( Carrasco et al. 2006) . This clean fuel implies a high reduction in production of pollutant gasses in areas where it is used. Additionally, the hydrogen can be used as fuel in cells that have similar characteristics as batteries, in powering electric motors. In each case, its production must incorporate power input. Due to a large amount of energy required to produce hydrogen, most of its production activities must be relocated to less populated areas ( Raupach et al., 2007) . There are a number of alternatives that can be used to produce hydrogen, for example, the use of solar power that has an ability to alter this stringent requirement for hydrogen production completely.
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