A Solar Energy Future? Solar Power Technologies

Here’s a map showing the latitudinal distribution of solar energy (W/m²) (Figure 1). One thing’s for sure, the solar energy supply is plentiful in most areas.

Figure 1: Distribution of average annual solar irradiance over the Earth’s surface (W/m²) (Source: Nelson et al, 2014)

Let’s power our future with solar energy! What do you think of solar power as a solution for CO₂ mitigation? Check out the ‘Discussions’ section of the blog for more on that kind of stuff and other energy debates.

The current post is part of the ‘Technologies Series’ of the blog, where reviews of the range of technologies already implemented, or currently being researched for energizing the future is provided.

For starters, let’s take a look at some of the solar technologies.

There are different types of solar energy conversion (Nelson et al, 2014):

- Solar Thermal (sunlight energy is converted to heat)

- Solar Photovoltaic (PV) (sunlight energy is converted to electrical work)

- Solar Chemical (sunlight energy is converted to stored chemical potential energy)

The main solar energy technologies are (Nelson et al, 2014):

-       Solar hot water systems

-       Concentrated solar thermal power

-       Solar Photovoltaics (Solar PV)

-       Solar cells

Solar hot water systems

These systems provide hot water for domestic and sanitary purposes and can be used to heat swimming pools (Nelson et al, 2014). They are also useful for heating and cooling spaces and applied for some industrial processes (Norton, 2014).

Technologies: Evacuated tube, glazed collectors; flat-plate glazed (panel) collectors; unglazed collectors. 

(Source: http://www.energymatters.com.au/solar-hot-water/solar-hot-water-works/)

Solar Hot Water System for the Home (Source:http://www.markgroup.co.uk/homeowners/solar/solar-hot-water)

[YOUTUBE VIDEO] - Solar Hot Water System in the Home!! https://www.youtube.com/watch?v=WoErOQB6Z7o

Concentrated solar thermal power

It’s in the name. Concentrating solar power (CSP) technology involves using mirrors to reflect sunlight and collect solar heat to generate electricity (Pierce, 2013). Solar energy is concentrated in several ways (IEA, 2009). Sunlight can be focused onto a linear receiver (Parabolic Trough/Linear Fresnel systems), or in the case of parabolic dish/engine and central receiver tower systems, the sunlight is focused to a point (Pierce, 2013).

(Source: CSP Global Outlook2009 cited by IEA (2009))

The concentrated solar energy is then used to efficiently heat a fluid to a high temperature and this drives a steam turbine/heat engine to generate electrical power (Nelson et al, 2014).

Storage system in a trough solar plant 

(Source: SolarMillennium cited by IEA CSP Technology Roadmap (2010))

[YOUTUBE VIDEO] 

Concentrated Solar Power Simple Explanation

https://www.youtube.com/watch?v=JbJ7AVHBQfs

Solar photovoltaics (Solar PV)

In this technology, sunlight (photons) are absorbed by semi-conductors (usually forming a p-n junction) to generate an electric current (RedArc Solar, 2014). The electricity can be used directly, stored in batteries or fed into the grid (Nelson et al, 2014). 

 

(Source: http://www.redarc.com.au/solar/about/solarpanels/) 

Semi-conductors make up the solar PV cell. The most common set up is the 2-layer module.

Here's a quick summary of the process (adapted from SolarEnergy.net, 2014): 

1. 2-layer PV cell 

2. One layer is positively charged; the other is negatively charged.

3. Solar energy (photons) are reflected, passed through or absorbed by the solar cell.

4. The negatively charged layer absorbs photons, until electrons are freed from the negatively charged semiconductor material. 

5. Electrons move to the positive layer ---->>> WEEEEEE!!!!!

6. A voltage differential is created. 

7. Layers connected to an external load. Electrons flow through a circuit to create electricity!!!!!

(Source: http://www.geoliving.co.uk/solar/photovoltaic-cells)

PV modules come in different designs. 

They are usually made from layers of a semi-conductor material, placed in between two contact materials that collect the electric current (Crystalline Silicon (c-Si) is the common material) (Nelson et al, 2014). 

Current research effort is targeted to finding different PV materials (e.g. thin films and high efficiency devices (multiple layers of different semi-conductors) (Nelson et al, 2014).

Solar PV can be in the following forms (Zeman, N.d.):

Stand-alone PV systems (AWWW....soooo lonely):  These rely on PV power only and may include a storage mechanism (e.g. batteries). 

Grid-connected systems: Connected to the grid through inverters. These systems don't need batteries – the grid gets all the electricity from the PV system directly. 

Hybrid systems: A combination of PV modules and electricity generators (e.g. wind generators).

For more advanced stuff on photovoltaic systems....<CLICK HERE>

Solar energy technologies can also be applied in other areas:

- Solar Fuel cells – see the 'Transition Energy' part of the blog website for more!! :) 

Here's a hint of what's to come....

In line with the ‘Sustainable Fuels Concept’ (Air Fuel Synthesis online, 2013), there is a strong incentive to develop fuels by converting CO₂ and water (H₂O) into synthetic hydrocarbon liquids (Jiang et al, 2010). The sun's energy is one way to drive the fuel synthesis process.

I’ll touch more on this later on solar cells (artificial photosynthesis) hydrogen fuel cells and energizing the future of transport. SOOOOO.... Stay tuned!

Check out the 'Transition Energy' part of the blog website for more!!! :) 

Just some things you may want to have a look at:

Air Fuel Synthesis online (2013) Renewable Energy for Liquid Fuels. Available at: http://www.airfuelsynthesis.com/ (Accessed: 28 December 2013)

Concentrating Solar Power: Global Outlook 09: Why Renewable Energy is Hot

IEA (2010) Technology Roadmap: Concentrating Solar Power 

IEA (2009) Renewable Energy Essentials:Concentrating Solar Thermal Power 

Jiang, X., Xiao, T., Kuznetsov, V.L. and Edwards, P.P. (2010) ‘Turning Carbon Dioxide into Fuel’, Philosophical Transaction of Royal Society A, 368, pp. 3343-3364.

Nelson et al (2014) Solar Power for CO2 Mitigation. Grantham Institute for Climate Change Briefing paper No 11. Imperial College London. 

Norton, B. (2014). Introduction. In Harnessing Solar Heat (pp. 1-8). Springer Netherlands.