Solar Thermal Cogeneration
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The STC Program provides documentation and other technical resources for building and maintaining STC systems.  The STC Program makes local production of solar-thermal cogeneration systems easier by making all technical information readily accessible.  The STC program promotes local economies and minimum-cost residential energy by enabling small-scale craftsman industry to supply residential energy systems.

The STC technical documentation includes resources for construction of new systems and also includes the complete maintenance history of deployed systems in the field.  Ideally the builder of a system provides ongoing maintenance for that system.  But others may assume maintenance using the online documentation, i.e. the maintenance schedule, the system ratings, and data for fabricating replacement parts.  This resolves for the owner the risk of runaway maintenance costs. 

The STC owner is responsible for verifying that a maintenance/repair procedure has been adequately documented on the website before paying the maintenance/repair fee.  Evidence that maintenance has been performed without proper update to the online documentation may result in the removal of the installation from the STC Program.

A wiki may be provided for documenting the design, construction and maintenance history of installations.  Directions of future expansion for the STC Program include optimizing the system for various climates and architectures, expanding into local raw materials production and recycling, reducing embedded costs of the systems, and energy-efficient residential appliances and workshop power tools.

Ways to Collaborate:  (start collaborating now)

  • build/maintain an STC for yourself
  • build/maintain STCs for others
  • employ someone to build/maintain an STC for you
  • line up funding for someone to build/maintain STCs
  • enroll in apprenticeship
  • contribute to design & documentation
  • train designers/builders/maintainers
  • supply materials/services to builders

Online Resources

Why Solar Energy?
The Permanent Energy Crisis
Global Warming 'Past the Point of No Return'
Nigeria militants say all oil producers at risk
Deregulation Hasn't Worked

Why/How Small-Scale Craftsman Industry?
Let the People Rebuild New Orleans
An "Ownership Society" on the Tigris
Do Your Part, the Way Co-op America Does
The Idea of a Local Economy
Inside Indonesia 59 - Blacksmith boom
Ghandi on Mass Production

Autonomous Residential Design
Autonomous Building
Passive Solar Home Design
Passive Solar Heating and Cooling
Natural Energy and Vernacular Architecture

Solar-Thermal Energy Resources
Power From The Sun
An Introduction to Solar Thermal Systems
Assessment of Solar Technology
SolarPACES Home Page
History of Solar Energy

Free/Open Technology Designs/Standards
Free Hardware Designs -
Introduction to Extending the Freedoms of Free and Open Information - "Historically in Europe and America, research universities have been funded by national and military interests who were not particularly disposed to the giving away of knowledge. However, only through sharing information did research move forward at an efficient pace."

Business Resources
Reference For Business - encyclopedic format references
US Industry Profile - encyclopedic format reference

Math/Physics/Engineering Resources - includes conversions
Wikipedia · derivatives · integrals
HyperPhysics · Internet Public Library
Factbites · Intute Ejournal Search Engines
NACA (Aeronautics) Technical Report Server
MIT Unified Engineering · Rice U. Connexions
DOE Fundamentals Handbooks · LLNL Reports
eFunda: Online Reference for Engineers · RoyMech
The Engineering Toolbox · ASME Standards
International Journal of Rotating Machinery
Fundamentals of Engineering Supplied Reference Handbook (pdf)
Energy Conversion Ebook

Fluid Mechanics/Steam
Spirax Sarco · Navier-Stokes Equations · IAPWS-IF97 formula
Fundamentals of Compressible Fluid Mechanics (pdf)

Solid Mechanics
Strength of Materials · Simple machines
Stress · Euler-Bernoulli beam equation
Tensor Calculus and Continuum Mechanics
Statics & Strength of Materials

Backyard Metalcasting · Machining and Metalworking at Home
Budget Casting Supply · Wikipedia Metalworking
Gingery Books · Rec.Crafts.Metalworking
Heat Treatment of Steel · Virtual Machine Shop


Platforms/Applications: GNU · Linux · Mozilla · XFIG · GnuPlot · Octave
Software Development: GCC · Glibc · GDB · DDD
Electronic Design Automation: gEDA · FreePCB · XCircuit · PCB
Instrumentation: Osqoop
Computational Fluid Dynamics: CFD Online - Links - Software
IRCnet webchat - Enter in your nickname and the agreed-upon channel at the agreed-upon time. 
Wiki - Software to provide server for documenting STC implementations and other collaboration.
Moodle - a course management system

Online Books/Journals

Project Gutenberg is working on a 1911 Encyclopedia Britannica conversion, Modern Machine Shop Practices, and other online books (title search, alt-interface).  Also see Free Science and Engineering books, Wikibooks, Universal Digital Library, The Online Books Page (search, archives),and Google Book Search.  For computer software texts see O'Reilly Open Books Project.

Engineering Methodology

A basic methodology for engineering is to:  A.) Using mental models, piece together a system with preliminary components/approaches and evaluate it.  B.) Make adjustments and modifications to components/approaches and evaluate the changed performance.  C.) Make a final selection and build a prototype.  D.) Evaluate the prototype performance and make final adjustments.  

Design Philosophy

Includes long lifespan for components; construction from a minimum variety of materials, as raw materials as possible, reliance on locally available materials and simple, low cost construction tools/methods; minimum embedded energy; continuous rather than intermittent operation of components; gradual changes for parameters under control, e.g. rotational speeds, temperatures, pressures; design simplicity for reliability, e.g., minimum use of auxiliaries such as valves, probes, throttles, clutches and gears; optimizations to minimize materials costs and maximize efficiency and reliability; use of digital control algorithms to increase efficiencies; unification/duality where possible to minimize the necessary volume of specialized knowledge, e.g. turbine/pump, motor/generator, AC/DC power conversion. 


The lifespan goal is three decades with the following maintenance schedule: 1.) reflector washing at two-month intervals, 2.) reflector polishing at one year intervals, 3.) turbine bearing lubricant and filter change at five year intervals, and 4.) turbine bearing change at decade intervals.  To meet this goal, and to support local craftsman industry, the STC design includes custom fabrication of most components.  The builder/maintainer should also remove and recycle the materials at the end of the system's lifespan.

Full Costs

The full costs of something include its purchase price, manufacturing cost, recycling/disposal cost, operating costs and reliability.  Purchase price may be presented as a cost per year by considering expected lifespan.  Manufacturing and recycling/disposal costs are costs borne by the public such as environmental damage, called externalities.  Operating costs include power consumption, and maintenance.  Reliability is affected by the complexity of a component which increases the probability of flaws, and also by the design and quality of materials.

Computer Technology

Image-processing with low-cost digital video and computer technology may be vital to ensuring system thermodynamic stability during intermittent cloud cover.  Advanced projects may include image processing for quality control of fabrication materials. Acoustic and vibration analysis techniques may be implemented to monitor the mechanical and thermal systems for both system control and failure prediction.  Acoustic flow measurement in pipes may be performed using a computer to transmit and detect a signal on the outside of a pipe.  The signal propagated in the fluid will arrive early or late depending on the fluid flow rate.  A low-cost computer-based oscilloscope and other instrumentation are good candidates for STC program projects.

The STC System design employs a computer to coordinate among the various subsystems.  Using a multi-tasking operating system the computer simplifies hardware implementation of complex control features.  The choice of an open processor design on programmable digital hardware enables optimizing the processor design for the application, enabling maximum efficiency in terms of development effort, cost of components and the system's energy consumption.  The procedure entails identifying and eliminating redundancy/waste of processor routines/resources, in executing the application-specific tasks. 

Meteorological Data

Hourly data (daylight hours only), ground level, U.S. National Solar Radiation Data Base: TMY2 Data Files (format)
ERBS satellite Earth exo-atmospheric solar irradiance from 1984 to 2003 illustrates stability: .doc fmt (try Abiword)
History : Weather Underground Graphs of historical data - select city, search for 'Average climate' in result page
U.S. Direct-Normal Solar Radiation Map (pdf)
U.S. Climatic Wind Data (pdf)
Climates of the world
NOAA Sunrise/Sunset Calculator

Thermal Applications

Space heating: Heating Degree Days is the number of degrees that a space must be heated to reach 65°F for a given day.  The HDD may be accumulated for a series of days to provide a measure of the heating requirement for that time period, typically for a month or a year.  The amount of energy required to heat the space depends on the climate, efficiency of the heating/insulation systems, and the volume of the space.  The average BTUs/HDD/ft² in the US in 1997 is around 10.  Passive solar design may reduce this to almost zero for individual structures but the average for new structures may be conservatively estimated as 6 BTUs/HDD/ft².  For a 1500 ft² space in an arid climate in a moderate latitude with max winter HDD of 17.7 the max daily energy requirement is 6 BTUs/HDD/ft² * 1500 ft² * 17.7 HDD = 159600 BTU = 159600 BTU/(3412 BTU/kWh) = 47 kWh = 84% of the prototypical system capacity of 56 kWh.

Comparing Your Home's Energy Use to Others
NCDC: Heating and Cooling Degree Day Data

Water heating: Average hot water demand has been measured in the US as 30 gal/day/person *.  If 50 total gallons of hot water are used daily, and the temperature is raised from 50°F to 140°F, the energy added is gallons *  specific heat of water * temp diff  = 50 gallons *  4.396 Wh/(gal*°K) * 50 °K = 11 kWh.

Space cooling:  Typical space cooling capacity utilized in the US is 1 ton of cooling per 1000 ft² of space, running 10 hours per day on peak cooling days, so a 1500 ft² space would use 1.5 tons 10 hours per day or 1.5 tons * 3.5 kW/ton * 10 hrs = 53 kWh.

Food refrigeration: 
The convection heat transfer rate through a container with 85 ft² of surface area, R-10 insulation, and temperature differential of 80 °F, is 85 ft² * 80 °F / R-10 = 640 Btu/h = 200 W.  In a day this equals 5 kWh.


Materials are a key concern of the STC program due to impacts on design feasibility, and health/environmental/social impacts.  Health/environmental impacts are minimized with careful control of liquid/vapor/dust generation, proper collection/disposal, and avoiding contamination of bodies, clothes and living spaces.  Environmental/social impacts are minimized by selection of materials verifiably produced with environmental/social responsibility.  (see: Safety / Environmental)

Materials science - Wikipedia · MatWeb · AZoM · eFunda · ASAP Source · Smorgon Steel Group · Embodied Energy of Some Materials

Materials Vendors

Materials should be obtained from local manufacturers who can assure quality and answer technical questions.  Some manufacturers better serve the goal of minimum-cost energy.  For example, STMicroelectronics minimizes the embedded energy in its products.  Some of the materials, e.g. steel, are manufactured to industry standards.  After selected a standard material one should request copies of the chemical composition reports from vendors and compare them to the standard specification before purchase.  Commercial labs can also verify chemical composition.
Materials Exchange

Materials Data

The following materials are noted for their versatility and other characteristics that help achieve STC system design goals.  Ideally, all materials are plentiful, locally-available, renewable and non-hazardous.  STC program goals regarding materials include minimizing the variety, quantity and cost of materials, easy access to complete/accurate bills of materials, and maintaining high-quality materials data.

Pure Water
is a clean, effective medium for heat transfer, e.g. in a steam system.  Pure water lacks the ions, dissolved gases, minerals and compounds commonly found in tap water and well water.  These impurities react with materials, interfere with heat transfer, and cause general mayhem in thermal and chemical processes.  Pure water is distilled, possibly several times, and deaerated for use in closed systems.  Distillation involves boiling and condensing, which removes ions, minerals, and compounds.  Deaeration is simply boiling to drive out dissolved gases immediately before adding to closed systems.  The purity might be determined by electrical resistance or pH.  Pure water containers should be clean.  Alternatives to distillation are generally unacceptable.  A solar still is cost-effective.  More on water distillation

Alcohol mixed with water is useful as a heat transfer medium at temperatures below the freezing point of water.  An alcohol/water mixture has a freezing point as low as -50°F, depending on the ratio of the mixture.   Alcohols are biodegradable.  Glycerol can be made by de-esterifying vegetable oil.   Advantages of glycerol include low toxicity, flammability and gaseous emissions. Disadvantages include a higher viscosity/pump load, and a tendency to leak at connections and loosen corrosion in lines.  Ethanol can be made by fermenting/distilling sugars.  Ethanol has lower viscosity, lower cost but higher toxicity, flammability and gaseous emissions at high temperatures.  Various salts may be used in low temperature heat transfer instead of alcohols and are low cost, non-toxic, and non-flammable but can be very corrosive.  More on: glycerol, ethanol · Selecting a Heat Transfer Fluid · preparing anti-freezing solutions

Ammonia is a natural compound with a low boiling point and is useful as a refrigerant in cooling cycles.  Ammonia is a natural byproduct of animal protein metabolism.  As a component of animal waste, ammonia provides a key nutrient (nitrogen) to plant life, as part of the natural cycle.  It is not damaging to the environment like refrigerants in compressor coolers.  If highly concentrated, ammonia is toxic to humans, but with adequate ventilation it evaporates quickly into the atmosphere.  More on ammonia · The manufacture of ammoniacal gas · Haber process

Cellulose fiber is an effective anti-convective insulation, made by finely shredding newspapers or other plant materials, e.g. cotton, straw and sawdust.  The character of the resulting fiber determines the most effective insulation, with paper fiber usually superior. Flame-retardants may be toxic.

Perlite is an inert volcanic glass of very low density, making an effective anti-convective insulation suitable for high temperatures, not vulnerable to fire or pests, and may be obtained commercially.  Embedded costs are greater than cellulose.

Argon gas, the third most abundant element in the atmosphere, is a good heat insulator due to low thermal conductivity.  Thermal conductivity of a gas is proportional to its specific heat and inversely to its molecular mass and collision diameter.  Argon gas has relatively large molecular mass and collision diameter.  Thermal conductivity is mostly independent of gas pressure above a very low pressure threshold.  Argon gas is non-toxic and inert and is fairly inexpensive via commercial sources.  More on argon gas

Borosilicate glass
, used in cookware, has high resistance to thermal shock, high strength at elevated temperatures, low chemical reactivity, low thermal expansion, and a transmittance of 0.9 to 0.93 across the solar spectrum (400-2000nm) for  thicknesses of several mm.  glass · glass properties · Schott · Coleparmer · QVF · Kavalier · Wilmad (pdf) · Mellesgriot (pdf)

Castor oil is extracted from the castor bean.  It is useful as a lubricant and heat-transfer medium.  Castor oil does not become excessively viscous at low temperatures; and it performs well as a high-temperature lubricant, well suited for use in jet, diesel, and race car engines.  Ricinoleic acid, a hydroxy fatty acid, makes up 85–90% of castor oil and is responsible for many of its desirable properties. - References for Castor Oil Facts · Castor Oil

Jojoba oil: The physical properties of jojoba oil are: high viscosity, high flash and fire point, high dielectric constant, high stability and low volatility. Its composition is little affected by temperatures up to 570°F (300°C).  The viscosity index of jojoba oil is much higher than that of petroleum oil; therefore, it may be used as a high temperature, high pressure lubricant. - *Jojoba oil can be used in various kinds of polishes, and insulation for batteries and electrical wires. - *

Wood can be a valuable alternative to metals for structural components and may help reduce full costs if selected carefully.  More on wood, lumber, list of woods

Rubber is an elastic polymer made from natural latex from sources such as the para rubber tree, useful for sealing and separating components.  It may be porous or non-porous depending on the fabrication process.  Raw rubber coagulates spontaneously from latex which may be sped up using acids such as vinegar or formic acid.  An alternative latex source is guayuleMore on natural rubber latex

Epoxy is a very strong, versatile general adhesive, binder for paints and primers, especially on corrosion-prone metal, high temperature range, excellent electrical insulator and mechanical binder, used in printed circuit boards and many electrical components.  Epoxy is generally more corrosion and chemical-resistant than other polymers but oxidizes under UV light. Different epoxy formulas bond better to different materials.  Elasticity may be required to accommodate material expansion/contraction under various influences.  Heat-cured epoxy may be necessary in high-temperature applications.  The humidity in the curing environment may be critical to performance.

A variety of commercial formulations pose varying health hazards, and many ingredients remain untested.  Vapors and liquid are hazardous before curing and dust is most hazardous after curing.  Gloves and masks minimize exposure to vapors and liquids.  Wet grinding cured epoxy and collecting the waste for hazardous disposal minimizes exposure to dust.  Using only solvent-free and additive-free formulations should reduce the hazards to those of the polymer itself.  Much research has been performed on Bisphenol-A, one of the resin options, and it's been found to have higher toxicity than thought before.

Epoxy is probably not necessary for paint binders in the STC but for securing magnets and coils in a high-speed generator, epoxy is probably necessary if the generator is to meet the target system lifespan.  Alternatively a more natural resin may be used and the generator rebuilt at certain intervals.  More on epoxy · Chemistry of Epoxies · Epoxy Resin Systems Hazard Evaluation (pdf)

Powdered Iron is useful for making electromagnetic coil cores for moderate rates of flux change.  Iron oxide (magnetite) may be collected from the ground with a magnet, ground up, and mixed with epoxy and molded into a core shape.  Powered iron is highly combustible.

Ferrite is useful for making electromagnetic coil cores and permanent magnets.  Powders of ferrous and dielectric materials are mixed and sintered in a mold.  To make permanent magnets, a more involved process is required.  More on Ferrite

Carbon Steel is strong, relatively inexpensive, and useful for moderate-temperature, clean steam and water plumbing, and for structural applications, having a high modulus of elasticity, for example More on carbon steel

4340 Steel is a high-tensile
(930 – 1080 Mpa) steel useful for high-speed rotor shafts.  More on 4340 steel, properties

Stainless Steel is a very strong alloy containing iron, carbon and chromium.  It is expensive but useful for high-temperature steam pipes, high speed rotors and other high temperature, high strength applicationsMore on stainless steel · type 304 · type 316  Welding, cutting, grinding, and polishing stainless steel can produce the irritant/carcinogen hexavalent chromium

416 Stainless Steel is a high-tensile
, high-temperature, corrosion resistant steel containing iron, carbon and chromium.  More on 416 stainless steel 

Copper is an excellent electrical and thermal conductor for use in electrical wiring and heat exchanger tubing More on copper

Aluminum is a strong, lightweight metal with good electrical and thermal conductivity and excellent electromagnetic reflectivity and thermal emissivity properties More on aluminum

Lead is a dense metal useful for making rechargeable battery plates More on lead

Sulfuric Acid
is an inorganic acid useful for a battery electrolyte.  More on sulfuric acid

Safety / Environmental

High speed, high temperature, high pressure systems require a routine maintenance/inspection schedule for detecting/repairing any problems that could compromise safety.

Store hazardous materials in sealed containers for re-use/recycling.  Work with local regulators to avoid potential hazards of various materials.  Obtain Material Safety Data Sheets from the manufacturers and research the safety hazards of individual ingredients in the materials and select materials and methods with these safety hazards in mind.

US EPA Household Hazardous Material Program
OSHA Technical Links to Safety and Health Topics


Fasteners are rated for tensile strength and shear strength in pounds per square inch (psi) of cross-sectional area.  For example, if a bolt is rated at 100k psi tensile strength and has a diameter of 0.25", then its tensile strength is 100k psi *[pi*(0.25/2)^2] = 4908 lbs. Tensile strength is the fastener's ability to withstand an axial, or stretching, force.  A threaded fastener's tensile strength is limited by the threads due to the reduced diameter at the threads.  Tensile strength is sometimes called ultimate strength.  Shear strength is the fastener's ability to withstand a force perpendicular to its axis.   These strength ratings indicate the point at which the fastener breaks.  Yield strength indicates the point at which the fastener permanently deforms and is always lower than the tensile strength.

Bolt Science · Tutorial
Grade 5 vs. Grade 8 Fasteners
Guide to Design Criteria for Bolted and Riveted Joints (pdf)

Structural Mechanics

A beam typically is suspended horizontally across two columns to support a gravitational load.  This load exerts a bending force on the beam which is compressive on the top face, tensile on the bottom face and neutral in the middle.  An I-beam design has increased strength for the same amount of material by decreased neutral material in the middle, and increased material on the top/bottom faces supporting the compressive/tensile loads.  Increasing the height of the I-beam, or distance between these faces, further increases the beam's strength by increasing second moment of area.  Trussed beam systems expand on this approach.  In such a system, a second beam runs parallel with the first beam.  A series of vertical and diagonal trusses connect the parallel beams, greatly increasing the the second moment of area of the beam system.

beam - bending
strut - compression
tie - tension

Tools / Techniques

An off-grid soldering station may be fueled by waste vegetable oil.  A tank, line and burner are needed, and a means of ventilation.  The station includes a sharp-tipped iron, with a thermocouple to measure its temperature, a vise, a reflector and lead-free soldier.   Welding is generally avoided in an effort to promote the off-grid shop. 

Creating A Vacuum - To evacuate a component, a small hole is drilled through the wall for evacuation, and a small metal tube is soldered into the hole.  A suction hose from a vacuum pump is connected to the end of the tube.  The component is heated to drive gases from the inside surfaces.  After the pump creates the desired vacuum the tube is sealed by crimping, leaving enough tube length to later repeat the process if necessary.  The tube is cut and the crimp is sealed with solder. Vacuum pump, Vacuum Basics, Refrigeration Service Pumps, High Vacuum with Mechanical Pumps (pdf), Pressure measurement

Electromagnetic Radiation, Transmission, Reflection, Absorption

Electromagnetic radiation is the influence of electron motion on other electrons across space and is a key mechanism of energy transport in nature, e.g. radiation from the Sun to planet Earth.  Solar radiation is mostly in the visible region of the spectrum while heat typically radiates in the infrared region.  When radiation impinges on groups of electrons, motional wave phenomena develop among the electrons.  Radiation is omnidirectional unless blocked or guided in certain directions. 

Electrons may be thought of as attached to atoms by springs that enable motion at a specific frequency, called the natural frequency.  Electrons attached to atoms in mixtures/molecules typically have mixed natural frequencies. Certain types and structures of atoms cause certain amounts of the electrons' motional energy to be absorbed by the atoms as heat.  Plant life manages to utilize this energy in the growth process.

When radiation impinges on electrons, that which is not absorbed by the atoms is transmitted or reflected at angles depending on the angle of incidence and on material characteristics.  In transmission/reflection, the electrons vibrate for a short period of time and then re-emit radiation. Transmission occurs when material characteristics allow interactions between electrons in adjacent layers of atoms through the material; To the degree that this interaction is inhibited and transmission is canceled by interference, the electrons in the surface layers reflect incident radiation.

An opaque mass transmits little radiation, so whatever isn't reflected is mostly absorbed.  A black mass reflects little visible radiation, but instead absorbs most radiation that impinges.  A white mass mostly reflects visible frequencies but randomizes the reflected direction so that optical images are not preserved (diffuse reflection).  Characteristic colors are typically exhibited by dielectric materials in which the electrons are tightly bound to the atoms.

A mirror surface mostly reflects all frequencies with a consistent angle by the uniformity of type and geometry of the surface layers of atoms (specular reflection), enabling optical images to be preserved.  These materials are typically metallic conductors with highly mobile electrons.  If a beam impinges on a mirror surface at an angle, then at the transmitted distance t and the reflected distance r, the radiation observed are approximately sums of functions of amplitudes, phases and distances, t and r, for each layer of atoms in the mirror.  The geometric regularity of atoms in metals, if preserved at mass boundaries, results in sequential patterns of amplitude and phase across the layers causing the functions to reinforce when the sequential distance decreases (reflection) while the functions cancel (interference) when the sequential distance increases (transmission). 

This interference in transmission within metallic masses is different from absorption in that absorption is a transfer of energy from electrons to nearby atoms, while interference only affects the electrons' ability to radiate composite energy along the transmission path.  The interference apparently works both ways, reducing radiation emission from the surface of the metallic mass.

Light Absorption, Reflection, and Transmission
Electromagnetic Waves
How does reflection work?
Light polarization and Fresnel laws
QED: The Strange Theory of Light and Matter

Physics Formulas

Image of Overall Heat Transfer

ideal gas pressure, temperature, mass, volume:
PV = nRT
PV = mMT
P = dMT these are consistent with the steam tables
P = pressure = force/area (N/m^2)
V = volume (m^3)
n = number of moles
R = 8.3145 J/mol K
T = temperature (K)
m = mass (kg)
M = 461.92 J/kg K (water: 1 mole = 18 g)
d = density = m/V (kg/m^3)

(IAPWS-IF97 formula ought to be much more accurate)

pressure, area, force, kinetic energy
P = F/A
K = FL
P = K/V
jK = PV
P = pressure = force/area (N/m^2)
K = kinetic energy = force*length (Nm)
F = force (N)
A = area (m^2)
L = length (m)
V = volume (m^3)

static pressure converted to kinetic energy through a nozzle
given pressure, energy rate, can find mass and volume rates from charts
given volume rate & nozzle area, you know velocity

T c  V c  M h    hurts pressure, saturates disks
T c  V c  M l  

T h V c M c hurts pipe
T l V c M c hurts efficiency
T c   V h   M c    longer evap  
T c V l M c longer evap

given temperature and volume you don't know pressure or mass, only their ratio
but adjusting the loads (no turbine, full condenser) you can measure velocity with tach

P = K/V and energy per mass (enthalpy) is known given pressure
P = m*v^2/2V
v = sqrt(2PV/m)

now energy per mass is known given the pressure

radiative heat transfer:
P = eaA(T^4-Tc^4)
e = emissivity (0-1)
a = stefan's constant 5.67 e-8 (w/m^2*K^4)
A = area
T = radiator temp (K)
Tc = environ temp (K)

Tsky = 270 K night


Copyright (c) 2005-2009 Robert Drury
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
See "GNU Free Documentation License". 

Disclaimer:  This information may contain inaccuracies and is provided
without warranty.  Safety first when working with high temperatures,
pressures, potentials, speeds, energies, various tools and materials.