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Functional Requirements of the Alphasole Prototype

French version here

Spanish version here

Design requirements

Within the scope of collaborative research, we work on the requirements of each element developped thereafter in the following sections. The discussion history between contributors is available through the links to the forum (in French):

L'historique des discussions entre contributeurs est accessible par les liens respectifs vers le forum :

General

Requirement Demonstrator Prototype Comments for protototype
Reduce risks Pay attention to parasitic reflexions * optical risks ; * risks related to high pressure and high temperature hydraulic circuit
Cost (material, production, manufacturing, assembling) Minimum Minimum: <300€/m² Savings possible with respect to demonstrator but not yet optimized

3) Concentrator optic

lien forum

Requirement Demonstrator Prototype Comments for protototype
Optical efficiency Reflectivity (at normal angle) 0.9 60-70% To fienetune: relevant/optimized geometry, cf cf discussion/forum ; reflectivity of mirrors >= 0.9 ; other parameters : fouling, cleaning frequency, evolution through lifetime
Robustness and lifetime no requirement 3 to 5 years To be studied : * time? * warranty? * what efficiency loss? * renewal point, maintenance frequency. * economic balance? * also to be written in other sections : structure, optic. *to define: expensive elements, frame elements last longer: 20 years or more
Accesibility for cleaning and maintenance no requirement yes *easy cleaning of the mirrors; *maintenance and tuning of the facets once mounted; *access to receptor once mounted
Thermal efficiency of the receptor secondary concentration on the receptor > 1.5 70-80% efficiency as a goal
Total concentration factor between 15 and 30 between 15 and 30 With 20 mirrors, it reaches about 15
Secondary reflector (CPC) : design coordinated with absorber 60% yes

Structure

Frame of mirrors set and receptor
Requirement Demonstrator Prototype Comments for protototype
Independant structure: mirror, receptor yes No Fixed relative position, to be set in accordance with latitude
Resistance to ambiant environment yes, punctually yes, permanently wind speed, hail, rain, snow, dust
Sufficient stiffness against vibrations and deformation yes yes
Ground fixing Adjustable feet Fixed Concrete base to be planned or fixation to an existing structure, roof… Study carefully stiffness, stability…
Assembling easiness yes yes kit possible
Transport easiness yes no
Welding the least possible Ok No requirement initially, compromise between : building complexity and assembling easiness
Limitation of accident risks yes yes at all stages : manufacturing, assembling
Structure of mirrors facets
Requirement Demonstrator Prototype Comments for protototype
Fresnel mirror: area 2×2 m$^2$ with 20 facets 10 cm widedefined by the power need (5KW )
Mirror deformation limitation deflection lower than 5 mm 0.1° facet orientation, respectively 1cm on the receptor (a priori) depends on receptor height, valid for 1.5m height
Sun tracking (east west) >120° respectively 8h tracking 12h tracking respective rotation of 90° in 12h
Bad weather protection yes yes for instance: 180° range (mirrors down)
Optical alignment possible through a tuning needless of special tools yes yesBetter: procedure to be updated for calibration
Easy switching of mirror facets yes yes more generally: easy maintenance

Système de suivi (Moteurs, Programme, Capteurs)

6) tracking system (engines, program, sensors)

lien forum

Requirement Demonstrator Prototype Comments for protototype
Real time accurate tracking of the sun motion yes yes
Motorisation of mirrors yes yes
Electricity consumption - Minimum achievable Plan an autonomous working mode (no connection to electical grid)? (photovoltaic pannel?)
Number of engines Minimum One per module or one for all the system To be validated regarding the other technical choices (structure)
Sun tracking to get the right angle yes yes, with necessary accuracy Goal: send all the beams of each mirror on the width of the recptor (CPC width)
Sensors (weather condition detection) - yes * ambiant temperature, direct sun radiation. (as a complement of process sensors (boiler and use))
Fluid temperature and pressure measurements yes drive the circulating pump controlled by pressure and/or temperature (according to use). Steam flow rate sensor? Liquid water level sensor? ⇒ depends on type of use
System automatic shutdown Optional Safety in case of electrical outage (circulating pump stopped ⇒ temperature increase) + in case of a storm (mirrors down (if possible)). (Resistance to hail?)
Simple controlling panel yes Programming expert mode when needed, but simple to use ideas: remote access ? consultation des informations de fonctionnement (et historique ?)To be scheduled

lien forum

Requirement Demonstrator Prototype Comments for protototype
Specific design for the working fluid, natural or forced circulation 100% yes
Selective material: High absorption qualities through all the solar spectrum : 100% , Absorbance 90%, infrared emissivity 15% : material intrinsically absorbant (or absorptive coating) = high absorbance through all the solar spectrum and low infrared emissivity
High thermal exchange between absorber and fluid 60% yes material and conduction-convection in the fluid
The system should be thermally insulated (with respect to ambiant air, infrared radiation) 60% yes see requirement for the overall thermal efficiency (insulation material above and glass below)
Good resistance to temperature variation (material expansion, tightness) 60% yes In particular, risks related to high temperatures and pressure of fluid

Ideas: * modularity is hardly compatible with the high constraints of the absorber (pressure, temperature variation etc.) * In case of frost, the absorber should be emptied (or the frost might destroy it). ⇒Ambiant temperature sensor + electric valve? ⇒design of the absorber enabling the complete emtying.

Usage

Requirements to be better defined with user

Functioning

Requirement Demonstrator Prototype Comments for protototype
Position: avoid building shadow and other masks - ?
Running range - ? *for a sun exposure not in first hour nor in last hour, *for which hour range in the day, in the season, * for which latitude
Temperature level - ? Optic and best technology may be different with respect to temperature. Example: *Hot water production at 80°C; *Steam production at 130°C from liquid water; *Steam Superheating from 150°C to 250°C
Hydraulic circuit
Requirement Demonstrator Prototype Comments for protototype
Pressure losses - Minimum Limit pressure losses, above all for light fluids : air, steam
Open/closed circuit - ?
Mineral scale risks - ? Gives good reason to run in a closed circuit…
Fluid - ?

Ideas: Could we have a feedback from the user? Which power (mini, maxi average) does he need? During how many hours? And for which season. At my parents', lavander distillery: July. Canned food and Jam from June to september.

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