PV Gap

Debbie Said:

Evaluate the advantages and disadvantages of using direct solar energy ?

We Answered:

The sun is providing free energy every day. How much energy depends mainly on the latitude and to some extent on climate. The question that you are asking is to evaluate our use of this energy to heat buildings and water and presumably other uses.

Advantages:

This energy is free at source and is totally renewable, as far as we know for thousands of years.

Disadvantages:

To harness this energy we need to employ materials and resources and to use our ingenuity to provide technical solutions appropriate to the economic and physical situation and location. There is a capital cost and possibly maintenance costs.

The actual harnessing of the energy can only happen in daylight hours so there may be problems of storing the energy at night.

The advantages are greatest in hot sunny climates but the need for energy is often greater in colder, northern or southern latitudes.

Methods

What are the methods that we can use? Where are the different methods most appropriate?

Buildings

For buildings we need to consider internal climate control and hot water supply and for both these we can use passive and active methods. It is also much easier to incorporate suitable provisions into new domestic, commercial and public construction, although significant improvements can be made to existing buildings.

Passive methods: The four methods for domestic construction in the northern hemisphere that make use of greenhouse effect are:
South facing windows (large windows on south, small or none on north side) other elevations as appropriate with solar shading or solar glazing and thermal insulation.
South facing roof space: usually pitched roof used as a solar collector. May need small fan and duct to circulate hot air.
Conservatory: South side glazed volume.
Trombe wall. South glazed wall with heavy masonry or concrete wall painted black.

And for larger buildings one might use a climate wall i.e. glazed external wall with significant air space between external and internal wall (internal wall can be fully or partially glazed or incorporate thermal mass for storage of heat)

Active methods use solar voltaic panels or solar collectors with water pumped to storage or direct use. Thermosiphon systems, where the storage tank is placed above the collector, do not need a pump and are therefore regarded as a passive system. Standard units are used for hot water supply throughout the Mediterranean countries and middle east. The use of thermal chimneys is also an anchient passive method of internal climate control with modern uses.

This is a very big subject and I have only touched on a brief outline. One could also discuss earth sheltering, construction methods, sustainability, low technology methods for emerging third world countries such as solar ovens and all sorts of related subjects.

Although all the above information is from my own personal knowledge, I have used references in the past such as Wikipedia, (on line encyclopaedia) the Energy Trust Website (a non- profit making Trust based in London) and for low cost energy saving
technology: http://www.energygreed.com/. This site offers a manual for building your own solar power array and wind turbine, with sources for free batteries and claims to save you 80% on electricity costs. In the future I think we will have better gas fired boilers that are not only more efficient like condensation boilers, but combine heating and power generation, so that you will be able to sell back your surplus electricity to the national grid in Britain or the power utility company in USA and Canada. Meanwhile we have to rely on the present technology and in cold climates improved insulation or more heavily insulated new construction, double or triple glazing. Solar methods can be quite useful depending on the payback period. Heat pumps with ground collection systems usually take longer to payback and depend on your having a large volume low energy heat source such as a large pond or coils in the ground. Wind energy is another useful method, and although intermittent can have an acceptable payback period.

Bertha Said:

Does anyone know any advantages to Solar Energy other then it saves you money and it is good for the earth?

We Answered:

right now the main source of energy on earth is fossil fuel
but how long can we burn fossil fuel?? 100 years?? 200 years??

fossil fuel will run out some day and you'll be forced to change your energy source such as hydro, solar, tidal, thermal...etc

solar is useful when it's day time because all you have to do is harvest the solar radiation waves which have been giving out by earth every second

no more machines are needed to convert the radiation into energy beside the solar panel, cable and an adaptor or power pack to store the energy been converted

this combination does not produce CO2, excess radiation or weird product

Dianne Said:

What advantages does solar energy have over fossil fuels?

We Answered:

It uses the suns energy without giving off carbon emissions.It is a self sufficient system using low maintenance.The suns rays penetrate the clouds even in winter usually 8hrs a day at 36,000,000 mtrs per sec.