Renewable energy

Today (12/3) we will…

Go test out our solar ovens :D

Learn about renewable energy

Renewable energy

What is renewable energy?

Renewable energy is energy from sources that are naturally replenishing but flow-limited.

Virtually inexhaustible in duration, but limited in amount of energy/time

Renewable energy investment

In the past, we’ve relied heavily on fossil fuels. Are they on the way out?

Types of renewable energy

Biomass energy is created from processing/refining biomass into ethanol and biodiesel

Is biomass better than fossil fuels?

Burning biomass also releases carbon into atmosphere

Depends on key factors:

How is the material harvested/processed?How long is the land given for recovery?

Modern carbon – carbon in biomass that was recently incorporated into plants

Fossil carbon – carbon from fossil fuels

Carbon neutrality

Fossil carbon has been buried for millions of years (burning it releases lots of excess CO2 into atmosphere)

Burning recently obtained carbon from plants will release CO2 that can be taken up by replanted organisms

What is biomass?

Harvesting solid biomass: Wood

Net removal - not allowing forest growth to keep up with forest use

Pros: Increase habitat diversity and increase total photosynthesis

Cons: Destroy habitats, increase erosion, increased water temp in water

Harvesting solid biomass: Manure

When wood is hard to find, people use manure (Africa, India)

Pros: Removes harmful microorganisms

Cons: Lots of death (1.5 mil) from increased pollutants - results in respiratory illnesses (cancer)

Today (12/5) we will…

Learn more about renewable energy

Revise projects

Biofuel: Ethanol

Ethanol is a sugar made from fermentation of starch/sugars in plants to alcohol and CO2

Materials: Sugarcane, wood chips, crop waste

90% of ethanol in the US made from corn and corn by-products

Biofuel: Ethanol

Gasohol: 10% ethanol and 90% gasoline

E-85: 85% ethanol and 15% gasoline

flex fuel vehicles: run on gas or E-85

Biodiesel: Ethanol

Pros: More “environmentally friendly” than gasoline

Cons: Carbon bonds in ethanol have less energy, so 90/10 gas reduces mileage by 2-3%, growing corn uses a lot of fossil fuels, takes a lot of land to grow corn

Biofuel: Biodiesel

Biodiesel – obtained by extracting oil from algae (very efficient) and plants (soy, palm) as a substitute for petroleum diesel

Diluted to “B-20”80% petroleum diesel20% biodiesel

Biofuel: Biodiesel

Pros: B-20 can be run by any diesel engine, CO (carbon monoxide) emissions are lower, contains modern carbon

Cons: Higher concentrations than B-20 only work in modified engines, more expensive than petroleum diesel

Hydroelectric power

Hydroelectricity – electric power created by the movement of water

2nd most common form of renewable energy (7% in US)

Factors affecting it:

Flow rate

Vertical distance of water falling

Types of hydroelectricity

Run-of-the-river system – water is kept behind a low dam and directed through a channel before returning to the river

Pros:

Little flooding upstream

Seasonal changes in river are not disrupted

Cons:

Smaller

Generation of electricity is irregular based on water flow

Water impoundant systems

Water impoundant systems – stores water behind a dam in resevior

Most common hydroelectric system

Pros:Water generation can be regulated

Cons:Disrupts ecosystems and natural habitatsDisrupts communities nearby

Tidal systems

Tidal energy - driven by gravitational pull of moon/sun (higher tides=more energy)

Tidal systems – utilizing gates/turbines to transfer kinetic energy from changes in tide to electricity

Cons:

Tidal power not suitable in places where tidal differences are small

Construction of transmission lines can disrupt marine ecosystems

Today (12/6) we will…

Finish up renewable energy

Listen to a TED talk on energy storage

Finish up design changes for tomorrow!

Hydroelectric pros/cons

Pros: -Renewable energy in developing countries-Minimal use of fossil fuels-No air pollution-Less costly than nuclear

Cons:-Forces people to relocate-Floods nearby land, affects downstream ecosystems-Construction utilizes greenhouse gases

Solar energy technologies

Active solar power – utilizing solar energy to power technology

Solar water heating – sun’s energy is absorbed by water and transferred to a water heating system

Active solar technologies

Photovoltaic (PV) solar cells – converts sun’s light energy into electricity. 12-20% efficient

Made of semiconductors that create electrical currents when exposed to light, converted to a higher voltage current for use

Active solar energy

Pros:

-No air pollution, water pollution

-Installing small scale PV panels can be less expensive if in a rural area

-Tax breaks, rebates and funding provided by government

Cons:

-Expensive to create and install, despite rebates

-Areas w/out sun generate little to no energy

-Toxic metals/chemicals used for building

Geothermal

Geothermal energy – energy created by heat emitted by the inside of Earth

Pros:

-Energy from Earth is non-depletable

Cons:

-Ground water is depletable

-Not all areas have active magma

-Hazardous gases and steam can be emitted from power plants

Nesjavellir Geothermal Power Station

Puna, Hawaii

Wind energy

Wind energy – warmer air rises and cooler air sinks. Creates wind patterns that move turbines to convert kinetic energy to electricity

Pros:

-No pollution

-Land can be shared w/other uses

-No fuel needed to maintain turbines

Cons:

-Most wind systems need batteries to store electricity

-Harms wild-life (40,000 birds killed/year in US)

-Aesthetically unpleasing

Kawailoa wind farm

Today (12/7) we will…

How do we get our electricity?

Finish up renewable energy

Watch a TED talk on renewable storage

It’s raining so we need to postpone the solar cooker test #2

The problem with renewable energy…

There are several main problems with renewable energy:

Costs

Land use

Reliability

Storage

The cost of renewable energy

Renewable energy is still more expensive to start than fossil fuels.

A large scale solar system might be around $2,000/kW, a natural gas plant around $1,000/kW to install.

However, over the lifespan, renewable energy comes out on top, with average costs around $30-50/MWh. Coal and gas come in around $40-80/MWh.

Land use

Renewable energy takes up a lot of land. Wind farms, solar fields, etc. take up much more land than coal mines.

To get a terawatt hour from coal, you need 9.7 square kilometers. For wind, 72 square kilometers.

The sun doesn’t shine all the time…

What happens when the wind doesn’t blow, the sun doesn’t shine, the tides don’t change?

You don’t get energy from renewables. How do we solve this problem?

Storage

Storage can be a solution to the reliability of renewable energy.

However, batteries that are cheap, hold a lot of energy and are scalable are difficult to build.

Batteries like lithium-ion (in your phones) won’t scale to that challenge (in grid level storage).

What will your future home look like?

Your future house