Renewable Energy

First law of thermodynamics

Conservation of energy

Second law of thermodynamics

Impossible to convert thermal energy with 100% efficiency

“Available” energy

Energy that is available at a relatively competitive cost

Pollutants involved in natural ambient air quality standards (criterion pollutants)

• SO2

• Nitrogen Oxides (NOx)

• Carbon Monoxide (CO)

• Ozone (O3)

• Particulate Matter (PM)

• Lead (Pb)

Why is CO2 not a criterion pollutant

It is so widespread government regulation would have a negative impact on all industries

Almost all renewable energy is produced for ______ barely any contributes to heating or industrial processes

electricity generation

5 steps of electric power generation

1. Generation station

2. Step-up transformer

3. Transmission lines

4. Step-down transformers

5. Customers

Generation Station

Consumes input energy and produces electrical power as outlet

Step-up transmission

Electrical power output is converted to higher voltages for efficient transmission

Transmission line

Carry electrical energy from the generating station to the electric grid

Step-down transformer

Voltage is converted to lower voltages useable by various consumers

Customers

Electric power consumers connected to the electric grid at different points

Force

Physical capacity required to change motion of an object

Equation to determine force

F= mass (kg) x acceleration (m/s2)

Energy

Capacity to work

Forms of energy

• Thermal

• Chemical

• Kinetic

• Gravitational

• Electrical

• Nuclear

• Renewables

What unit of thermal energy is commonly used in power plant design

BTU - British Thermal Units

Power

The rate at which energy is being converted (consumed)

Equation for power P (W)

P (W) = Energy (J)/time (s)

Units for electrical power

(KW) or (MW)

Equation for energy

Energy (J) = Power (W) x Time (s)

Plant heat rate (a measured quantity)

Amount of thermal energy in BTU required to generate 1kWh of electrical energy with the fuel used in that plant

Why can’t you determine exact heat rate before something is built?

Even if the thing you are building is identical, operating conditions (temp, terrain, etc) change the result —> you suppliers can have bonuses or penalties for not providing promised rate

Conversion for kWh to BTU

1 kWh = 3,412 BTU

Plant efficiency (output over input)

(Amount of BTU in 1 kWh) / (Heat rate - measured)

Capacity factor

Ratio of actual ANNUAL energy production to annual rated energy production (considers actual usage conditions) (measured/rated)(actual/theoretical)

Capacity factor equation

(Actual annual energy production) / (power (rated) x 8760 hrs per yr)

Do you want a high or low capacity factor?

High

How do you increase a capacity factor

Improve operating conditions (ex: move a wind turbine offshore)

What are the basic voltages for generation, transmission, and distribution

1. Output of commercial generating system = ~12,000V

2. Voltage stepped up (transformers) = ~120,000+V (or 235 kV)

3. Voltage stepped down (substations) = ~12,000V (local dist.)

4. Voltage stepped down further for consumer use = ~120-600V

Why is voltage stepped up for transmission?

To reduce energy loss when traveling over a long distance

Electrical grid

Interconnected network of generating stations and electrical power consumers

Blackout/overload

When power production cannot meet power demand

4 major interconnections (grids)

• Western interconnection

• Eastern connection

• Electric reliability council of Texas

• Quebec interconnection

7 balancing areas among grids

WECC, MRO, TRE, NPCC, SPP, SERC, FRCC

What are balancing areas

smaller partitions of the grid for better management of power distribution and safety functions

What is the basic trading unity of the U.S. electricity market

Locational Market Price (LMP)

How is LMP determined?

Via internet-based auction that maximizes PARTICIPANT BENEFITS (will find lowest cost for need and benefit seller at same time)

What are the two types of U.S. energy markets/settlement processes?

1. Day-Ahead: Put in order 24 hrs ahead (better pricing)

2. Real-Time: Need energy now (lack of planning costs more) (every 5 min)

Do other countries have an electricity market?

No - it’s typically supplied by the government

Locational Market Price (LMP)

Cost of supplying the next increment of electric demand at a specific location (node, bus, substation) in the network

• units = $/MW hour

What do wholesale power price maps display

Real-time constraints on transmission of electricity

What are LMP’s determined by?

• Supply offers and demand bid to buy energy

• Losses and constraints on transmission circuits

What happens to price when supply is less than demand

Price increase

Equation for LMP

LMP = Cost to produce (generation marginal cost) + Cost to transmit (transmission congestion cost) + Cost to transmission losses (cost of marginal losses)

Turbine

Takes in high-pressure steam and rotates shaft

Generator

Spun by shaft (has central magnet that lines up electrons when it rotates)

What are the two basic turbine types

Gas and steam

4 steps of power generation in a PULVERIZED COAL PLANT

1. Pulverized coal burned in a steam generator (producing steam)

2. Steam admitted to to the steam turbine at high temperature and high pressure (critical or super critical)

3. Steam expands the turbine and this expansion drives the turbine and generator to produce energy

4. Expanded steam is condensed to water in the condenser and then returned to the steam generator (boiler)

3 Steps of air pollution control in a pulverized coal plant

1. Flue-gas from the combustion of goal in the steam generator is passed through an electrostatic precipitator to remove particulates

2. Flue-gas then passes through a flue-gas desulfurization (FGD) unit (or scrubber) to remove SO2 from the gas

3. After scrubbing, the flue-gas is exhausted through a stack

How does the FGD scrubber work

gas is mixed with limestone which reacts with SO2 and is collected as a solide or liquid slurry

Steps of simple cycle combustion (GAS) turbine

1. Intake air compressed, mixed with gas fuel, and burned in the combustion chamber

2. Hot gases from combustion chamber expand through a turbine which turns an electric generator to produce electricity

3. Hot exhausted gas is typically let out into the atm (67% waste heat)

4. ~50% of turbine is used to drive air compressor (back to first step) - also takes away from efficiency (have to spend energy to get energy

Characteristics of simple cycle combustion turbines

• Mature tech, low capital cost

• Short design and installation schedules

• Rapid startup times and high reliability

• High operation and maintenance costs and therefore only used for peaking operation

• Small size (less than 300 MW)

• Can also burn liquid fuels like petroleum oil

Describe a natural gas combined cycle (NGCC) plant

• Includes simple cycle gas turbine

• Includes a steam turbine plant

• Heat from hot gases of combustion is captured in heat recovery steam generator (HRSG) producing steam which is passed through a steam turbine generator

• Steam turbine drives the second generator using the captured energy

Characteristics of NGCC plant

• Low emissions

• Significantly higher efficieny than combustion turbine along (~60% efficiency is possible) —> exhaust heat from CT captured rather than lost to the atmosphere

• Capital operation and maintenance (O&M) costs are HIGHER than separate systems