1. Distributed Generation: An Introduction

Anne-Marie Borbely and Jan F. Kreider

2. Combustion Engine Generator Sets

Eric Wong, Herb Whitall, and Paul Dailey

3. Combustion Turbines

Richard Brent

4. Photovoltaic Systems

Yogi Goswami and Jan F. Kreider

5. Microturbines

Colin Rodgers, James Watts, Dan Thoren, Ken Nichols, and Richard Brent

6. Fuel Cells

Jacob Brouwer

7. Principles of Control of Distributed Generation Systems

Peter S. Curtiss

8. Economic and Financial Aspects of Distributed Generation

Ari Rabl and Peter Fusaro

9. The Regulatory Environment

Morey Wolfson

10. Combined Heat and Power (CHP)

Bruce Hedman and Tina Kaarsberg

11. Electric Power Distribution Systems

Lawrence A. Schienbein and Jeffrey E. Dagle

12. Installation and Interconnection

James M. Daley and Anne-Marie Borbely

13. Fuels

Branch Russell, Don Stevens, and Michael Godec Nomenclature

This book is dedicated to Billy, who had the vision.


A Annual payment

A Area, m2

Alife Levelized annual cost

Am Annual cost for maintenance, first-year $

(A/P, r, N) Capital recovery factor

AFUE Annual fuel utilization efficiency, %

Cbase Base level energy (hot water, cooking, lights, etc.), kWh/yr

Ccap Capital cost, first-year $

Draft coefficient for resistance to airflow between floors Effective heat capacity of building, J/°C Concentration of pollutant (for example, SO2), |g/m3 Life cycle cost Salvage value, first-year $ Normalized annual consumption Cooling load factor at time t Cooling load temperature difference at time t, °C Coefficient of performance Consumer price index Cost

Heat capacity, kJ/°C Specific heat, kJ/(kg - K) Distance, km Diameter, meters

Cooling degree-days for base Tbal, °C-days Heating degree-days for base Tbal, °C-days Radiation emissive power, W/m2 Blackbody emissive power, W/m2 Emission rate of pollutants, g/kWh dep Present value of total depreciation as fraction of Ccap fd n Depreciation during year n as fraction of Ccap




Clife C




CDD(Tbai) HDD(Tbai) E

Epol f fl g

glo, hor glo, vert

Ktot k kT L

Lat Long



max pdem

Fraction of investment paid by loan Acceleration due to gravity = 9.81 m/s2 Extraterrestrial daily irradiation, MJ/m2 Daily global irradiation at earth's surface, MJ/m2 Daily global irradiation on vertical surface, MJ/m2 Heating values, J/kg Enthalpy, kJ/kg

Height, meters (use appropriate subscripts) Hydraulic head referring to pressure, meters Convection heat transfer coefficient, W/(m2 - °C) Indoor surface heat transfer coefficient, W/(m2 - °C) Outdoor surface heat transfer coefficient, W/(m2 - °C) Extraterrestrial irradiance, W/m2 Diffuse irradiance on horizontal surface, W/m2 Beam (direct) irradiance at normal incidence, W/m2 Global horizontal irradiance, W/m2 Global irradiance on tilted plane, W/m2 Joules

Conductive heat transmission coefficient, W/°C

Daily solar clearness index

Monthly average solar clearness index

Total heat transmission coefficient of building, W/°C

Thermal conductivity, W/(m-°C)

Instantaneous or hourly clearness index

Load, kW

Latitude, deg

Longitude, deg

Mass, kg

Mass flow rate, kg/sec System life, yr

Number of hours per bin of bin method

Depreciation period, yr

Pressure, Pa

Present worth factor

Peak demand, kW

Demand charge, $/kW/month

Part load ratio o


Price of energy, $/GJ


Levelized energy price, $/GJ


Price of insulation, $/m2


Energy consumption, Joules


Heat flow, watts


Annual energy, kWh


Shading coefficient


Seasonal energy efficiency ratio


Solar heat gain factor, W/m2


Seasonal performance factor




Entropy, kJ/(kg -°C)


Temperature, R or °C


Dry-bulb air temperature, °C


Balance-point temperature of building, °C


Indoor air temperature, °C

1 tstat

Thermostat setpoint temperature, °C


Outdoor air temperature °C

Ao, ave

Average outdoor temperature on design day, °C

o, max

Design outdoor temperature, °C


Sol-air temperature, °C


Sol-air temperature of outside surface at time t, °C


Average outdoor temperature for any hour t of month, °C

o, yr

Annual average temperature, °C


Solar time, h


Sunset time, h


Overall heat transfer coefficient, W/(m2 - °C)


Wind speed, m/s


Flow rate, m3/s or liters/s


Volume, liters


Velocity, m/s


Work, kJ


Thickness of wall, ft (in)


Distance, meters


Annual yield

Greek a Absorptivity for solar radiation

P Grid penetration, fraction

Ap Pressure differential

AT Indoor/Outdoor temperature difference, Ti - To, °C

At Time step h

Ax Thickness of layer, meters

5 Solar declination, degrees n Efficiency

8i Incidence angle of sun on plane, degrees

8p Zenith angle of plane (tilt from horizontal, up > 0), degrees

8s Zenith angle of sun, degrees

X Latitude p Density, kg/m3

pg Reflectivity of ground

Azimuth angle of plane, degrees Azimuth angle of sun, degrees

Conversion Factors

1 meter = 3.2808 ft = 39.37 inches 1 km = 0.621 miles

1 kJ/kg-°C = 0.23884 Btu/lbm^F 1 kW = 3412 Btu/hr 1 watt = 1 joule/second 1 HP = 550 ft-lbf/s = 746 watts 1 Quad = 1015 Btu °F = °G1.8 + 32

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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