Solar Drying Technology

Tri Ratna Bajracharya, Ph.D. Center for Energy Studies (CES)

Institute of Engineering/TUPulchowk, Lalitpur

Training on Strengthening the Capacity of Tumba College of Technology, Rwanda

Lecture 6: Solar Thermal Technology

Solar Box Dryer

Solar Cabinet Dryer

Solar Tunnel Dryer

Solar Dryers Developed by RECAST

1. Solar Box Dryer

2. Solar Cabinet Dryer

3. Solar Tunnel Dryer

4. Hybrid Solar Biomass Cabinet Dryer

1. Solar Box Dryer

Simple dryer, consisting of a rectangular box, insulated at its base and covered with a transparent glass sheet.

Holes are drilled through the lower front side to permit fresh ventilating air entry into the box.

Air outlet chimney is located at the top

S.N Parameters Improved Design

1 Mode of drying Direct

2 No. of glazing Single

3 Incoming air Not preheated

4 Loading provision Pulling the drawer from backside

5 Air outlet provision Chimney at the top

6 Air circulation Natural

7 Glazing slope 20 degree

8 Collector area 1m2

9 Drying capacity 4 kg-fresh

10 Construction materials

Wood, aluminum sheets, glass sheet, G. I. sheet and glass wool

11 Approximate cost NRs. 8000

1. Solar Box DryerSpecifications

2. Solar Cabinet DryerConsists of two separate

parts:

(a) a collector: to heat the air from ambient temperature to a desired temperature with the help of solar radiation, and

(b) a drying chamber with a stand and a chimney

The commodities to be dried are spread on a number of trays at different layers.

S.N

Parameters Improved Design

1 No. of glazing Single

2 Incoming air Preheated

3 Loading provision

Opening of complete doors at backside

4 No. of trays 9

5 No. of doors 3

6 Air circulation Natural

7 Height of stand 1m

8 Collector area 3.2m2

9 Drying capacity 10 kg-fresh

10 Construction materials

Wood, steel section, aluminum sheets, glass sheet, G.I. sheet and glass wool

11 Approx. cost NRs. 45000

2. Solar Cabinet Dryer

Specifications

Consists of a series of collectors and drying trays arranged in a particular order.

Air, sucked into the system by an electric blower

placed at the air exit of the dryer, is heated in the collector and flows over the products spread in thin layers on the trays.

3. Solar Tunnel Dryer

S.N Parameters Improved Design

1 Mode of drying Direct

2 No. of glazing Single

3 No. of trays 32

4 Air circulation Forced, 373W, A. C.

5 Air outlet provision

Without chimney and venturi unit

6 Collector area 24m2

7 Drying capacity 70 kg-fresh

8 Construction materials

Wood, steel section, G.I. sheet, aluminum sheets, glass sheet and glass wool

9 Approx. cost NRs. 200000

3. Solar Tunnel DryerSpecifications

Thank You!