Space P

Secondary

Batteries

Super Caps

Reversible Fuel Cells

Regenerative Fuel Cells

EnergyWheels

-Battery charge control

-Battery discharge control

- Voltage regulator

Regulate the bus voltage to the required voltage level

- Regulate the power output (voltage and current) from solar cells and energy storage systems

- Regulate the voltages during charging of energy storage systems

Provide direct current (DC)or alternating current (AC)

DC

Low power demands

Low transmission distances

AC

High power demands

High transmission distances

Batteries, fuel cells, solar cellsproduce direct current(DC)

PPT - explanation

When a load is directly connected to the solar panel, the operating point of the panel will rarely be at peak power. The impedance seen by the panel determines the operating point of the solar panel. Thus by varying the impedance seen by the panel, the operating point can be moved towards peak power point. Since panels are DC devices, DC-DC converters must be utilized to transform the impedance of one circuit (source) to the other circuit (load). Changing the duty ratio of the DC-DC converter results in an impedance change as seen by the panel. At a particular impedance (i.e. duty ratio) the operating point will be at the peak power transfer point. The I-V curve of the panel can vary considerably with variation in atmospheric conditions such as irradiance and temperature. Therefore, it is not feasible to fix the duty ratio with such dynamically changing operating conditions.

3000 m² - 250 kW

Power <1kW

+

-Independence of power production from S/C orientation

-Independence of the distance to the Sun -> deep space missions are possible

-Suitable for mission with long eclipse period (lunar landers, etc.)

-No storage required for shadow eclipse

-

-Adversely effect the radiation environment of the S/C -> RTG needs to be deployed on a boom away from the S/C bus

-Careful handling procedures during S/C integration (radioactive source!)

-Potential of dispersing in the atmosphere in case of launch failure

“The Safety analysis report prepared for the US energy department came to the conclusion that the risks are extremely small and well understood. It‘s much more likely someone will be injured driving a car to protest a RTG launch than in an RTG dispersion accident.”

lithium ion - 100 - 265 Wh /kg

k

NiCd

NiH2

LiIon

NiMH

Li-poly

-Exhibits memory effect,

-Environmental concerns (Cd)

-Extensively used till mid-1980s

28-32 Wh/ kg

-No memory effect,

-Highly reliable operation

35-65 Wh/kg

-Extensively used since mid-1980s

Very sensitive to over-charge and over discharge, -> Needs complex charge control for high number of single cells

-High self-discharging rate @ high temperatures

-Energy density degradation over time independent on use

-Often over 50% degradation after 150 cycles at temperatures <-5°

-mission @ low cycle life-temperature problems-small satellites, short mission time

70 - 150 Wh

- Performance temperature dependent

-Under evaluation (ESA, ESTEC)

100-200 Wh

R-SOFC: Regenerative Solid Oxide Fuel Cell fuel cells (R-FC)

Reversible fuel cell reaction, one unit

generating electricity in fuel cell mode (producing H2O or CO2)

separating water in H2/O2in electrolyze mode -> energy storage!

or: separating Carbon dioxide in CO/O2 -> energy storage & O2production

Flywheels

low mass, high cycle life, capable of being integrated, autonomy, peak power, capable of discontinuous charging, volume

Short term missions:

   -Primary batteries -Fuel cells

Long term missions:

   -Solar photovoltaic systems combined with secondary (rechargeable) batteries for energy storage

Outer-/inner planets:

   -e.g. Radioisotope Thermoelectric Generator (RTG)

Very high power demand

   Nuclear reactor -Solar-dynamic generator (heat?)